9 files changed, 522 insertions, 21 deletions
diff --git a/content/posts/2006-03-19-openvpn-article-in-linux-magazine.html b/content/posts/2006-03-19-openvpn-article-in-linux-magazine.html
index 319dd7e..18026de 100644
--- a/content/posts/2006-03-19-openvpn-article-in-linux-magazine.html
+++ b/content/posts/2006-03-19-openvpn-article-in-linux-magazine.html
@@ -5,8 +5,21 @@ title: OpenVPN Article in Linux Magazine
 
 <p>
 On the off-chance you haven't heard about it yet, I wrote an article
-on <a href='http://openvpn.net/'>OpenVPN</a> for <a href='http://www.linux-mag.com/'>Linux Magazine</a>.  
+on <a href='https://openvpn.net/' title='OpenVPN'>OpenVPN</a> for <a
+  href='https://web.archive.org/http://www.linux-mag.com/'
+  title='Linux Magazine'
+>Linux Magazine</a>.
 It's in the April 2006 issue, which has already been mailed to subscribers and should be available at
 bookstores and on newsstands any day now.
 </p>
 
+<p>
+<b>Update (2025-06-08):</b> Hello from 19 years later!  The
+<a
+  href='https://web.archive.org/'
+  title='Wayback machine'
+>Wayback Machine</a> has an archived copy of the 2006 article: <a
+  href='https://web.archive.org/web/20070812003116/http://www.linux-mag.com/id/2502'
+  title='Casting Your Net with OpenVPN'
+>Casting Your Net with OpenVPN</a>.
+</p>
diff --git a/content/posts/2023-05-02-bookworm-and-podman.md b/content/posts/2023-05-02-bookworm-and-podman.md
index 63b842d..485f03a 100644
--- a/content/posts/2023-05-02-bookworm-and-podman.md
+++ b/content/posts/2023-05-02-bookworm-and-podman.md
@@ -9,7 +9,7 @@ a great release.
 
 I've been looking for a suitable [Docker][] replacement for a few years
 because of [their repeated license shenanigans][license-shenanigans].
-Last year I tried switching to [Podman][], but ran into into several
+Last year I tried switching to [Podman][], but ran into several
 incompatibilities and minor annoyances.
 
 [Podman 4.3][podman-4.3] ships with [Bookworm][] and seems to fix all
diff --git a/content/posts/2023-12-02-firefox-redux.md b/content/posts/2023-12-02-firefox-redux.md
index 28e51f9..75d78ef 100644
--- a/content/posts/2023-12-02-firefox-redux.md
+++ b/content/posts/2023-12-02-firefox-redux.md
@@ -21,10 +21,12 @@ Chrome to [Firefox][].  Thoughts so far...
 
 ### Firefox Cons
 
-- No tab groups.  ~~There are several tab management extensions, but none
-  are as elegant as tab groups.~~ (**Update:** [Tab Stash][] is a
-  passable alternative for me).
-- Occasional [screen tearing][] on complex pages.
+- ~~No tab groups.  There are several tab management extensions, but none
+  are as elegant as tab groups.~~ **Update:** Firefox 136 added tab
+  groups.  I also like the [Tab Stash][] extension.
+- Occasional [screen tearing][] on complex pages.  I think this is an
+  artifact of Firefox in [X11][], because it does not happen under
+  [Wayland][].
 - Chrome has smoother scrolling.
 
 I also worry about [Mozilla][] as an organization; a substantial portion
@@ -57,7 +59,10 @@ monopoly to an advertising company.
    interface, supports [uBlock Origin][].  I've used it for years on my
    phone and tablet.
 
-**Update (2023-12-04):** Added note about [Tab Stash][].
+Updates:
+- 2023-12-04: Added note about [Tab Stash][].
+- 2025-06-07: Added note about Tab Groups in Firefox 136 and clarify
+  that screen tearing only happens in [X11][].
 
 [ublock origin]: https://en.wikipedia.org/wiki/UBlock_Origin
   "Free and open source browser extension for content filtering and ad blocking."
@@ -104,5 +109,7 @@ monopoly to an advertising company.
   "Portable Document Format (PDF)"
 [tab stash]: https://addons.mozilla.org/en-US/firefox/addon/tab-stash/
   "Tab Stash extension for Firefox"
-
-
+[x11]: https://en.wikipedia.org/wiki/X_Window_System
+  "X Window System"
+[wayland]: https://en.wikipedia.org/wiki/Wayland_(protocol)
+  "Wayland"
diff --git a/content/posts/2025-05-18-onion-service-mirror.md b/content/posts/2025-05-18-onion-service-mirror.md
index 053a76f..13bfca6 100644
--- a/content/posts/2025-05-18-onion-service-mirror.md
+++ b/content/posts/2025-05-18-onion-service-mirror.md
@@ -1,27 +1,25 @@
 ---
 slug: onion-service-mirror
-title: "Onion Service Mirror"
+title: "Tor Site Mirror"
 date: "2025-05-18T09:44:21-04:00"
 ---
-This site is now mirrored as an [onion service][] at the following
-([Tor][]-only) [URL][]:
+This site is now mirrored on the [Tor network][] at the following
+[onion address][]:
 
-[http://pabstordmsrzhushs5drpb5mtb2ml56iyacidsjfebl2jlss65rlbsqd.onion/][pabstor]
+[http://pablotronfils76sk6pwvyoosvfjbhxe3sn4c654e4na4szidbnbqdyd.onion/][pablotron.onion]
 
 See [Site Backend - Onion Service][site-backend-onion-service] for more
 details.
 
-[tor]: https://torproject.org/
+**Update (2025-06-02):** New [vanity .onion address][].
+
+[tor network]: https://torproject.org/
   "The Onion Router"
-[onion service]: https://community.torproject.org/onion-services/
-  "Service that can only be accessed via the Tor network."
-[pabstor]: http://pabstordmsrzhushs5drpb5mtb2ml56iyacidsjfebl2jlss65rlbsqd.onion
-  "Onion service URL for this site."
+[pablotron.onion]: http://pablotronfils76sk6pwvyoosvfjbhxe3sn4c654e4na4szidbnbqdyd.onion/
+  "Site mirror onion address."
 [site-backend-onion-service]: {{< relref "articles/site-backend" >}}#onion-service
   "Site Backend, Onion Service"
-[url]: https://en.wikipedia.org/wiki/URL
-  "Uniform resource locator (URL)"
-[.onion]: https://en.wikipedia.org/wiki/.onion
+[onion address]: https://en.wikipedia.org/wiki/.onion
   "Top-level domain for onion services."
 [mkp224o]: https://github.com/cathugger/mkp224o/
   "Vanity .onion address generator"
diff --git a/content/posts/2025-06-07-uninstall-facebook.md b/content/posts/2025-06-07-uninstall-facebook.md
new file mode 100644
index 0000000..904d43b
--- /dev/null
+++ b/content/posts/2025-06-07-uninstall-facebook.md
@@ -0,0 +1,132 @@
+---
+slug: uninstall-facebook
+title: "Uninstall Facebook"
+date: "2025-06-07T18:08:27-04:00"
+---
+You should immediately remove the Facebook and Instagram apps from
+your Android devices:
+
+> We disclose a novel tracking method by Meta and Yandex potentially
+> affecting billions of Android users. We found that native Android
+> apps—including Facebook, Instagram, and several Yandex apps including
+> Maps and Browser—silently listen on fixed local ports for tracking
+> purposes.
+>
+> ...
+>
+> This web-to-app ID sharing method **bypasses typical privacy
+> protections such as clearing cookies, Incognito Mode and Android's
+> permission controls. Worse, it opens the door for potentially
+> malicious apps eavesdropping on users’ web activity.** (emphasis mine)
+
+[Source][local mess]
+
+[Ars Technica][] also has [an excellent summary][].
+
+In English: If you have the Facebook app or Instagram app installed on
+your Android device, then Meta may have secretly collected your identity
+and your browsing history.
+
+This is true even if you don't have a Facebook account.  It's true even
+if you don't use the Facebook app.  It's true even if you took steps to
+hide your browsing history like clearing cookies or using a private
+browser window.
+
+On June 3rd, Meta claimed that the code responsible had "been almost
+complete removed"; this is [weasel wording][] which actually means "the
+code has not been removed".
+
+Even if Meta actually did remove the code from their apps, there are
+still several problems:
+
+1. Meta has an [atrocious privacy record][].  It would be foolish to
+   take Meta at their word and they have a strong incentive to try
+   this again or something similar in the future.
+2. Removing code does not address the information Meta has already
+   collected.  This information could be leaked in a data breach or
+   subpoenaed by law enforcement.
+3. Malicious or [trojaned][] apps could listen on the same local ports
+   and collect the same information.  The [Local Mess][] researchers
+   demonstrated this with a proof-of-concept app.
+
+Additional privacy recommendations:
+
+1. Prefer web sites over apps.  Many services use [deceptive patterns][]
+   to trick you into using an app instead of a web site.  They do this
+   because an app can collect more information about you than a web site.
+2. Remove unused and rarely used apps.
+3. Stop using Google Search.  I recommend [DuckDuckGo][].
+4. [Stop using Google Chrome][ditch-chrome].  I recommend [Firefox][]
+   with [uBlock Origin][] and some [configuration
+   changes][firefox-privacy].  Some folks swear by [DuckDuckGo Browser][],
+   but I haven't used it myself.  See also: [The case for ditching
+   Chrome][vox-chrome].  If you really do need Chrome or Edge, then at
+   least install [uBlock Origin Lite][].
+5. Switch from Microsoft Windows to [Linux][].  I recommend [Ubuntu][]
+   for new users.  I use [Debian][debian].  If you really do need
+   Windows, then at least [disable Windows telemetry][].
+6. Switch from text messaging and WhatsApp (owned by Meta) to [Signal][].
+7. Set up [Pi-hole][] on your home network.  It has an easy-to-use web
+   interface and can help block ads and tracking on mobile devices and
+   "smart" TVs.
+8. Consider [Tor Browser][] or [Tails][] if the you need more protection
+   and are willing to accept some tradeoffs.
+
+Further reading: [Surveilance Self Defense][ssd]
+
+[local mess]: https://localmess.github.io/
+  "Local Mess: Tracking method used by Facebook, Instagram, and Yandex Android apps which bypasses privacy protection."
+[atrocious privacy record]: https://en.wikipedia.org/wiki/Privacy_concerns_with_Facebook
+  "Privacy concerns with Facebook (Wikipedia)"
+[ars technica]: https://arstechnica.com/security/2025/06/meta-and-yandex-are-de-anonymizing-android-users-web-browsing-identifiers/
+  "Ars Technica"
+[an excellent summary]: https://arstechnica.com/security/2025/06/meta-and-yandex-are-de-anonymizing-android-users-web-browsing-identifiers/
+  "Ars Technica: Meta and Yandex are de-anonymizing Android users’ web browsing identifiers"
+[weasel wording]: https://en.wikipedia.org/wiki/Weasel_word
+  "Weasel word: Word or phrase aimed at creating an impression that something specific and meaningful has been said, when in fact only a vague, ambiguous, or irrelevant claim has been communicated (Wikipedia)"
+[fingerprint]: https://www.amiunique.org/fingerprint
+  "fingerprint"
+[trojaned]: https://en.wikipedia.org/wiki/Trojan_horse_(computing)
+  "Trojan horse (Wikipedia)"
+[firefox]: https://www.mozilla.org/en-US/firefox/new/
+  "Mozilla Firefox web browser"
+[ublock origin]: https://en.wikipedia.org/wiki/UBlock_Origin
+  "uBlock Origin ad-blocker"
+[ditch-chrome]: {{< relref "posts/2023-12-02-firefox-redux.md" >}}#why-ditch-chrome
+  "Why Ditch Chrome?"
+[brave]: https://en.wikipedia.org/wiki/Brave_(web_browser)
+  "Brave web browser"
+[duckduckgo browser]: https://duckduckgo.com/app/
+  "DuckDuckGo web browser"
+[firefox-privacy]: https://cyberinsider.com/firefox-privacy/
+  "Firefox Privacy Checklist"
+[duckduckgo]: https://duckduckgo.com/
+  "DuckDuckGo search engine"
+[tor browser]: https://www.torproject.org/download/
+  "Tor Browser"
+[tor network]: https://www.torproject.org/
+  "Tor network"
+[linux]: https://en.wikipedia.org/wiki/Linux
+  "Linux operating system"
+[debian]: https://debian.org/
+  "Debian Linux"
+[ubuntu]: https://ubuntu.com/
+  "Ubuntu Linux"
+[disable windows telemetry]: https://windowsreport.com/disable-windows-11-telemetry/
+  "Disable Windows 11 telemetry"
+[pi-hole]: https://en.wikipedia.org/wiki/Pi-hole
+  "Pi-hole"
+[raspberry pi]: https://en.wikipedia.org/wiki/Raspberry_Pi
+  "Small single-board computer."
+[signal]: https://signal.org/
+  "Signal secure messenger"
+[ssd]: https://ssd.eff.org/
+  "Surveilance Self Defense"
+[tails]: https://tails.net/
+  "Tails: portable operating system that protects against surveillance and censorship"
+[vox-chrome]: https://www.vox.com/technology/387375/google-chrome-antitrust-privacy-android
+  "The case for ditching Chrome (vox.com)"
+[ublock origin lite]: https://en.wikipedia.org/wiki/UBlock_Origin#uBlock_Origin_Lite
+  "Manifest V3 version of uBlock Origin for Google Chrome, Microsoft Edge, and other Chromium-based browsers."
+[deceptive patterns]: https://www.deceptive.design/types
+  "Types of deceptive patterns"
diff --git a/content/posts/2025-06-08-armbian-on-odroid-n2l.md b/content/posts/2025-06-08-armbian-on-odroid-n2l.md
new file mode 100644
index 0000000..3443adf
--- /dev/null
+++ b/content/posts/2025-06-08-armbian-on-odroid-n2l.md
@@ -0,0 +1,145 @@
+---
+slug: armbian-on-odroid-n2l
+title: "Armbian on Odroid N2L"
+date: "2025-06-08T15:31:00-04:00"
+
+pics:
+  n2l:
+    css: "image"
+    tip: "Odroid N2L running Armbian."
+    sources:
+      - "/files/posts/armbian-on-odroid-n2l/n2l-1024.webp"
+      - src: "/files/posts/armbian-on-odroid-n2l/n2l-1024.png"
+        width: 1024
+        height: 771
+---
+
+Last week I installed [Armbian][] on an [Odroid N2L][].  The
+installation steps, installation results, and fixes for some problems
+are documented below.
+
+### Installation
+
+1. Download and import the [signing key][armbian-key] (fingerprint
+   `DF00FAF1C577104B50BF1D0093D6889F9F0E78D5`): \
+   `wget -O- https://apt.armbian.com/armbian.key | gpg -- import -`
+2. Download the current "Debian 12 (Bookworm)" image and the [detached
+   signature][asc] from the "Minimal/IOT images" section of the [Armbian
+   Odroid N2L page][armbian-n2l].
+3. Verify the [signature][asc]: \
+   `gpg --verify Armbian_community_25.8.0-trunk.8_Odroidn2l_bookworm_current_6.12.28_minimal.img.xz{.asc,}`
+4. Uncompress the image: \
+   `unxz Armbian_community_25.8.0-trunk.8_Odroidn2l_bookworm_current_6.12.28_minimal.img.xz`
+5. Flash the uncompressed image to a [microSD][] card: \
+   `sudo dd if=Armbian_community_25.8.0-trunk.8_Odroidn2l_bookworm_current_6.12.28_minimal.img of=/dev/sda bs=1M status=progress`
+6. Mount the second partition of the [microSD][] card on `/mnt/tmp`: \
+   `sudo mount /dev/sda2 /mnt/tmp`
+7. Use the instructions and template from [Automatic first boot
+   configuration][armbian-autoconfig] to populate
+   `/mnt/tmp/root/.not_logged_in_yet`.  My populated autoconfig is
+   [here][populated-autoconfig], but **it did not work as expected**;
+   see below.
+8. Unmount the second partition of the [microSD][] card.
+9. Insert the [microSD][] card into the [Odroid N2L][] and power it on.
+
+### Installation Results
+
+Worked as expected:
+
+- Successfully booted.
+- Successfully connected to [WiFi][] on first boot.
+
+Did not work as expected:
+
+- Did not connect to WiFI on subsequent boots.
+- Did not set the root password.  Instead the root password was `1234`.
+- Did not set the user password.
+- Did not set the user SSH key.
+
+### Fixes
+
+To correct these problems I connected a keyboard and monitor and did the
+following:
+
+1. Logged in as `root` with the password `1234`.
+2. Changed the root password and the user password.
+4. Edited `/etc/netplan/20-eth-fixed-mac.yaml` and fixed the
+   errors.  The corrected version is below.
+5. Ran `netplan apply` to apply the corrected network configuration.
+6. Rebooted to confirm that networking was working as expected.
+
+Here is the corrected `/etc/netplan/20-eth-fixed-mac.yaml`:
+
+```yaml
+network:
+  version: 2
+```
+&nbsp;
+
+After fixing networking, I did the following:
+
+1. Copied my SSH key.
+2. Edited `/etc/ssh/sshd_config` to disable root logins and password
+   logins.
+3. Ran `apt-get update && apt-get upgrade`.
+4. Installed `unattended-upgrades`.
+5. Rebooted to pick up the latest updates.
+
+<!--
+
+### Conclusion
+
+Many non-[Pi][] [SBCs][sbc] manufacturers stop providing software
+shortly after the hardware is released.  Owners are stuck with
+unsupported hardware running out-of-date software.
+
+Case in point: The latest download on the [Odroid N2L wiki][] is Ubuntu
+22.04.
+
+I'm thrilled that [Armbian][]
+
+original unused blather ...
+
+[Armbian][] now supports the [Odroid N2L][] as a [community maintained
+target][armbian-n2l].
+
+Context: A couple of years ago Nadine bought me a pair of [Odroid
+N2Ls][odroid n2l].  [Pi 4s][pi] were scarce because of supply chain
+issues, and the [Odroid N2L][] seemed like a decent substitute.
+
+The problem with non-[Pi][] [SBCs][sbc] is that the manufacturers
+invariably stop providing software updates shortly after release, so you
+are stuck with unsupported hardware running an out of date OS.
+
+As of this writing, the [Odroid N2L wiki][] still has the same software
+that it did when first got the hardware: Ubuntu 22.04.
+-->
+
+[{{< pe-figure "n2l" >}}][n2l-pic]
+
+[armbian]: https://www.armbian.com/
+  "Linux for ARM development boards"
+[odroid n2l]: https://www.hardkernel.com/shop/odroid-n2l-with-4gbyte-ram/
+  "Odroid N2L ARM A73 SBC"
+[pi]: https://en.wikipedia.org/wiki/Raspberry_Pi
+  "Raspberry Pi"
+[sbc]: https://en.wikipedia.org/wiki/Single-board_computer
+  "single-board computer (SBC)"
+[armbian-n2l]: https://www.armbian.com/odroid-n2l/
+  "Armbian for the Odroid N2L"
+[odroid n2l wiki]: https://wiki.odroid.com/getting_started/os_installation_guide#tab__odroid-n2l
+  "Odroid Wiki: Odroid N2L"
+[n2l-pic]: /files/posts/armbian-on-odroid-n2l/n2l.jpg
+  "Odroid N2L running Armbian"
+[armbian-autoconfig]: https://docs.armbian.com/User-Guide_Autoconfig/
+  "Armbian Documentation: Automatic first boot configuration"
+[asc]: https://en.wikipedia.org/wiki/Pretty_Good_Privacy#Digital_signatures
+  "Detached PGP signature"
+[armbian-key]: https://apt.armbian.com/armbian.key
+  "Armbian PGP signing key"
+[populated-autoconfig]: /files/posts/armbian-on-odroid-n2l/odroid-n2l-root_not_logged_in_yet.txt
+  "Populated automatic first boot configuration file"
+[microsd]: https://en.wikipedia.org/wiki/SD_card#microSD
+  "microSD memory card"
+[wifi]: https://en.wikipedia.org/wiki/Wi-Fi
+  "Wireless networking"
diff --git a/content/posts/2025-06-08-nginx-caching-and-security-headers.md b/content/posts/2025-06-08-nginx-caching-and-security-headers.md
new file mode 100644
index 0000000..54cd4a0
--- /dev/null
+++ b/content/posts/2025-06-08-nginx-caching-and-security-headers.md
@@ -0,0 +1,27 @@
+---
+slug: nginx-caching-and-security-headers
+title: "Nginx Caching and Security Headers"
+date: "2025-06-08T13:16:00-04:00"
+---
+
+Yesterday I ported the [caching and security headers][apache-config]
+from the [Apache][] configuration for the public site to the [Nginx][]   
+configuration for the [Tor mirror][].
+
+The caching headers are particularly helpful for the [Tor mirror][].
+
+The updated [Nginx][] configuration and additional documentation are
+here: [Site Backend - Onion Service][onion-service].
+
+[apache-config]: {{< relref "articles/site-backend" >}}#apache-configuration
+  "Site Backend - Apache Configuration"
+[apache]: https://apache.org/
+  "Apache web server"
+[nginx]: https://nginx.org/
+  "Nginx web server"
+[onion-service]: {{< relref "articles/site-backend" >}}#onion-service
+  "Site Backend - Onion Service"
+[tor mirror]: {{< relref "posts/2025-05-18-onion-service-mirror" >}}
+  "Tor Site Mirror"
+[tor network]: https://torproject.org/
+  "Tor project"
diff --git a/content/posts/2025-06-08-old-openvpn-article.md b/content/posts/2025-06-08-old-openvpn-article.md
new file mode 100644
index 0000000..67f2ccf
--- /dev/null
+++ b/content/posts/2025-06-08-old-openvpn-article.md
@@ -0,0 +1,36 @@
+---
+slug: old-openvpn-article
+title: "Old OpenVPN Article"
+date: "2025-06-08T11:52:22-04:00"
+---
+
+In 2006 [I wrote an article about OpenVPN][article-post] for the
+now-defunct [Linux Magazine][].  This week I found a copy of the 2006
+article on the [Wayback Machine][]:
+
+[Casting Your Net with OpenVPN (Wayback Machine)][article]
+
+In 2025 you should prefer [Wireguard][] over [OpenVPN][] because
+[Wireguard][] is [faster, more secure, and easier to use][wg-reasons].
+
+Fun factoid: The [AWS Client VPN][] is just an [AWS][]-branded build of
+the [OpenVPN][] client.
+
+[article-post]: {{< relref "posts/2006-03-19-openvpn-article-in-linux-magazine" >}}
+  "OpenVPN Article in Linux Magazine" 
+[linux magazine]: https://web.archive.org/http://www.linux-mag.com/
+  "Linux Magazine"
+[wayback machine]: https://web.archive.org/
+  "Wayback Machine"
+[article]: https://web.archive.org/web/20070812003116/http://www.linux-mag.com/id/2502'
+  "Casting Your Net with OpenVPN (Wayback Machine)"
+[aws]: https://aws.amazon.com/
+  "Amazon Web Services (AWS)"
+[aws client vpn]: https://aws.amazon.com/vpn/client-vpn-download/
+  "AWS Client VPN"
+[openvpn]: https://openvpn.net/
+  "OpenVPN"
+[wg-reasons]: {{< relref "posts/2021-11-06-wireguard-is-awesome" >}}
+  "Wireguard is Awesome"
+[wireguard]: https://wireguard.com/
+  "Wireguard"
diff --git a/content/posts/2025-10-04-polycvss-v0.2.0.md b/content/posts/2025-10-04-polycvss-v0.2.0.md
new file mode 100644
index 0000000..49d20f7
--- /dev/null
+++ b/content/posts/2025-10-04-polycvss-v0.2.0.md
@@ -0,0 +1,143 @@
+---
+slug: polycvss-v0.2.0
+title: "polycvss v0.2.0"
+date: "2025-10-04T03:15:48-04:00"
+---
+I just released [polycvss][] version 0.2.0.
+
+[polycvss][] is a [Rust][] library to parse and score [CVSS][] vector
+strings.
+
+Features:
+
+- [CVSS v2][doc-v2], [CVSS v3][doc-v3], and [CVSS v4][doc-v4] support.
+- Version-agnostic parsing and scoring [API][].
+- Memory efficient: Vectors are 8 bytes. Scores and severities are 1 byte.
+- No dependencies by default except the standard library.
+- Optional [serde][] integration via the `serde` build feature.
+- Extensive tests: Tested against thousands of vectors and scores from
+  the [NVD][] [CVSS][] calculators.
+
+Here is an example tool which parses the first command-line argument as
+a [CVSS][] vector string, then prints the score and severity:
+
+```rust
+use polycvss::{Err, Score, Severity, Vector};
+
+fn main() -> Result<(), Err> {
+  let args: Vec<String> = std::env::args().collect(); // get cli args
+
+  if args.len() == 2 {
+    let vec: Vector = args[1].parse()?; // parse string
+    let score = Score::from(vec); // get score
+    let severity = Severity::from(score); // get severity
+    println!("{score} {severity}"); // print score and severity
+  } else {
+    let name = args.first().map_or("app", |s| s); // get app name
+    eprintln!("Usage: {name} [VECTOR]"); // print usage
+  }
+
+  Ok(())
+}
+```
+&nbsp;
+
+Here is the example tool output for a [CVSS v2][doc-v2] vector string, a
+[CVSS v3][doc-v3] vector string, and a [CVSS v4][doc-v4] vector string:
+
+```sh
+# test with cvss v2 vector string
+$ cvss-score "AV:A/AC:H/Au:N/C:C/I:C/A:C"
+6.8 MEDIUM
+
+# test with cvss v3 vector string
+$ cvss-score "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
+9.8 CRITICAL
+
+# test with cvss v4 vector string
+$ cvss-score "CVSS:4.0/AV:L/AC:H/AT:N/PR:N/UI:P/VC:L/VI:L/VA:L/SC:H/SI:H/SA:H"
+5.2 MEDIUM
+```
+&nbsp;
+
+This example tool is included in the [Git repository][] as
+[`src/bin/cvss-score.rs`][cvss-score].
+
+### Links
+
+- [polycvss Git repository][polycvss]
+- [polycvss package on crates.io][crates-io-polycvss]
+- [polycvss API Documentation on docs.rs][docs-rs-polycvss]
+
+**Updates**
+
+- 2025-10-12: [polycvss v0.2.1][]: Add [`polycvss::v4::Nomenclature`][v4-nomenclature] and improve documentation.
+- 2025-10-18: [polycvss v0.3.0][]: Add user-friendly `Error` messages, remove unreleased CVSS v2.x `Version` variants, and improve documentation.
+- 2025-10-19: [polycvss v0.3.1][]: Documentation improvements.
+- 2025-11-16: [polycvss v0.3.2][]: Add `impl From<Vector> for Severity`
+  and `examples/` directory.
+
+[html]: https://en.wikipedia.org/wiki/HTML
+  "HyperText Markup Language"
+[rust]: https://rust-lang.org/
+  "Rust programming language."
+[cvss]: https://www.first.org/cvss/
+  "Common Vulnerability Scoring System (CVSS)"
+[doc-v2]: https://www.first.org/cvss/v2/guide
+  "CVSS v2.0 Documentation"
+[doc-v3]: https://www.first.org/cvss/v3-1/specification-document
+  "CVSS v3.1 Specification"
+[doc-v4]: https://www.first.org/cvss/v4-0/specification-document
+  "Common Vulnerability Scoring System (CVSS) version 4.0 Specification"
+[bit-field]: https://en.wikipedia.org/wiki/Bit_field
+  "Bit field (Wikipedia)"
+[cvss-score]: https://github.com/pablotron/polycvss/blob/main/src/bin/cvss-score.rs
+  "Example command-line tool which parses a CVSS vector and prints the score and severity to standard output."
+[git repository]: https://github.com/pablotron/polycvss
+  "polycvss git repository"
+[polycvss]: https://github.com/pablotron/polycvss
+  "polycvss Rust library"
+[v2-calc]: https://nvd.nist.gov/vuln-metrics/cvss/v2-calculator
+  "NVD CVSS v2 calculator"
+[v3-calc]: https://nvd.nist.gov/vuln-metrics/cvss/v3-calculator
+  "NVD CVSS v3 calculator"
+[v4-calc]: https://nvd.nist.gov/site-scripts/cvss-v4-calculator-main/
+  "NVD CVSS v4 calculator"
+[cargo]: https://doc.rust-lang.org/cargo/
+  "Rust package manager"
+[podman]: https://podman.io/
+  "Podman container management tool"
+[docker]: https://docker.com/
+  "Docker container management tool"
+[api]: https://en.wikipedia.org/wiki/API
+  "Application Programming Interface (API)"
+[linter]: https://en.wikipedia.org/wiki/Lint_(software)
+  "Static code analysis tool to catch common mistakes"
+[src-v2-rs]: src/v2.rs
+  "CVSS v2 parsing and scoring"
+[src-v3-rs]: src/v3.rs
+  "CVSS v3 parsing and scoring"
+[src-v4-rs]: src/v4.rs
+  "CVSS v4 parsing and scoring"
+[nvd]: https://nvd.nist.gov/
+  "National Vulnerability Database (NVD)"
+[cvss-calcs]: https://github.com/pablotron/cvss-calcs
+  "Generate random CVSS vector strings and score them."
+[crates.io]: https://crates.io/
+  "Rust package registry"
+[docs-rs-polycvss]: https://docs.rs/polycvss
+  "polycvss API documentation on docs.rs"
+[crates-io-polycvss]: https://crates.io/crates/polycvss
+  "polycvss on crates.io"
+[serde]: https://serde.rs/
+  "Rust serializing and deserializing framework."
+[polycvss v0.2.1]: https://github.com/pablotron/polycvss/releases/tag/0.2.1
+  "polycvss version 0.2.1"
+[polycvss v0.3.0]: https://github.com/pablotron/polycvss/releases/tag/0.3.0
+  "polycvss version 0.3.0"
+[polycvss v0.3.1]: https://github.com/pablotron/polycvss/releases/tag/0.3.1
+  "polycvss version 0.3.1"
+[polycvss v0.3.2]: https://github.com/pablotron/polycvss/releases/tag/0.3.2
+  "polycvss version 0.3.2"
+[v4-nomenclature]: https://docs.rs/polycvss/latest/polycvss/v4/enum.Nomenclature.html
+  "polycvss::v4::Nomenclature documentation."