@misskey-dev/summaly is a tool for getting a summary of a web page. Starting in version 3.0.1 and prior to version 5.2.1, a logic error in the main `summaly` function causes the `allowRedirects` option to never be passed to any plugins, and as a result, isn't enforced. Misskey will follow redirects, despite explicitly requesting not to. Version 5.2.1 contains a patch for the issue.
https://github.com/misskey-dev/summaly/security/advisories/GHSA-7899-w6c4-vqc4
https://github.com/misskey-dev/summaly/commit/45153b4f08a772c395a13f7a25399dd87ed022ed