Add "Discord sex" post

content/blog/discord-sex-hack/index.md

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+---
+
+title: How the "Discord sex" (`s/e/x`) hack works
+date: 2022-05-11T21:11:17-05:00
+lastmod: 2022-05-11T21:11:17-05:00
+toc: true
+comments: true
+
+authors:
+  - bbaovanc
+
+categories:
+  - tips-and-tricks
+
+tags:
+  - discord
+  - discord-tricks
+  - sed
+
+# this will be shown for the article in list pages and in the page metadata
+# it can be either an image or video (this might change in the future, however)
+resources:
+  - name: feature
+    src: example.webp
+    title: Result after sending a GIF and then sending `s/e/x`.
+
+  - name: double-sex
+    src: double-sex.webp
+    title: Resulting image after typing `s/e/x` a second time.
+
+  - name: chess
+    src: chess.webp
+    title: This happens once you type `s/w/ag` after having done `s/e/x`.
+
+---
+
+There's this trick going around on Discord recently where if you send any GIF
+from Tenor, and then type `s/e/x`, then it turns it into a different meme GIF.
+Here's how it works.
+
+<!--more-->
+
+## The `sed` syntax
+
+For operating systems based on Unix or Linux, there's usually a simple terminal
+command included called [`sed`][sed-wikipedia], which is most commonly used to
+run text replacement commands. Here's a very simple example of what a basic
+`sed` command looks like:
+
+[sed-wikipedia]: https://en.wikipedia.org/wiki/Sed
+
+```console
+$ sed 's/hello/goodbye/'
+```
+
+For whatever reason, Discord decided to implement this into both their
+web/desktop client and their iOS app. Note that while real `sed` commands can
+get much more complicated, Discord's implementation doesn't support those
+advanced features[^trailing-slash-note].
+
+[^trailing-slash-note]: Also note that in Discord's implementation, the trailing
+  slash (after `goodbye`) can be ommitted (making it just `s/hello/goodbye`),
+  but with the real `sed` command, it's required.
+
+{{< see-also "/blog/text-substitution-in-discord-using-sed" >}}
+
+## What does `s/e/x` do?
+
+When you send a GIF using the GIF picker on Discord, it actually sends the link
+to the GIF, which is served by [Tenor][tenor-website]. For example, here's a GIF
+sent from Tenor:
+
+[tenor-website]: https://tenor.com
+
+https://tenor.com/view/cat-massage-gif-24282757
+
+Running `s/e/x` will take the first occurrence of `e` and replace it with `x`.
+The link becomes the following (notice the bolded letter `x`):
+
+[https://t**x**nor.com/view/cat-massage-gif-24282757][example-1]
+
+[example-1]: https://txnor.com/view/cat-massage-gif-24282757
+
+Then, all that's left to do is to buy the domain `txnor.com`, and write a simple
+program to run on it. In fact, it looks like that domain was purchased purely in
+order to make this trick possible[^txnor-domain-date].
+
+[^txnor-domain-date]: According to [a quick WHOIS lookup][txnor-whois], the
+  domain was registered on May 3, 2022. That's the same day that [@Rebane tweeted
+  about the new feature][rebane-tweet] (going to https://txnor.com redirects to
+  this tweet), so I assume that this is the only reason they bought the domain.
+
+[txnor-whois]: https://www.whois.com/whois/txnor.com
+[rebane-tweet]: https://twitter.com/rebane2001/status/1521544722875142145
+
+## How does it display on Discord without redirecting?
+
+When viewing any of the URLs on `txnor.com` in a normal web browser, you get
+[redirected to a tweet][rebane-tweet]. However, Discord is able to display the
+image without being redirected.
+
+When Discord loads a website to generate an embed, it uses a user
+agent[^user-agent-definition] (which is a little piece of text which tells the
+server what your browser is) which looks something like this:
+
+[^user-agent-definition]: If you actually care, there's a [Wikipedia
+  article](https://en.wikipedia.org/wiki/User_agent), and a [page on
+  WhatIsMyIPAddress.com](https://whatismyipaddress.com/user-agent) which also
+  explain what a user agent is.
+
+```text
+User-Agent: Mozilla/5.0 (compatible; Discordbot/2.0; +https://discordapp.com/)
+```
+
+The important part here is the word `Discord`. If you visit the website with
+your user agent set to anything containing `Discord` (case-insensitive), then it
+serves the image directly.
+
+### Double sex
+
+If you then run `s/e/x` a second time, then it changes to a different image:
+
+{{< figure src="double-sex" >}}
+
+This works in a simple way as well. The next `e` that appears in the URL is
+inside `/view/`. So, after typing `s/e/x` a second time, the URL becomes:
+
+[https://txnor.com/vi**x**w/cat-massage-gif-24282757][example-2]
+
+[example-2]: https://txnor.com/vixw/cat-massage-gif-24282757
+
+### Chess (`s/w/ag`)
+
+Another cool feature is that you can play chess by typing `s/w/ag` after typing
+the initial message of `s/e/x`.
+
+{{< figure src="chess" >}}
+
+## Extra features
+
+I'll update this section if I find out about any new features worth mentioning
+in the future.