Okay, have just submitted a PR to a fediverse project to fix a critical security vulnerability; CVE score is like 9.9/10.
More news once administrators of this servers using this project can upgrade safely.
Update: CVE was in @pixelfed, and the advisory is published here: https://github.com/pixelfed/pixelfed/security/advisories/GHSA-gccq-h3xj-jgvf
Have submitted confidentially pull requests that fix both their main branch and currently released version.
(yes, I manually backported the fix from main branch to their last release because the vulnerability is that critical to fix)
Awaiting response from the project maintainers now.