BigBlueButton is an open-source virtual classroom. In versions prior to 3.0.19, the recording playback (presentation format) was not sanitizing user's input in public chat. This allowed for a malicious actor to craft and carry out a targeted XSS attack, activated on anyone replaying the recording. This issue has been fixed 3.0.19.
https://github.com/blindsidenetworks/scalelite/releases/tag/v1.7.0
https://github.com/bigbluebutton/bigbluebutton/security/advisories/GHSA-8vv7-vj94-q2pv
https://github.com/bigbluebutton/bigbluebutton/releases/tag/v3.0.19
https://github.com/bigbluebutton/bigbluebutton/commit/69f45aa1b963dc7d80179d0155acc670aec5c4fc
https://github.com/bigbluebutton/bbb-playback/commit/09e89bfe4ff8488b68c3ff040d3081e419dc89b1