BigBlueButton is an open-source virtual classroom designed to help teachers teach and learners learn. An attacker with a valid join link to a meeting can trick BigBlueButton into generating a signed join link with additional parameters. One of those parameters may be "role=moderator", allowing an attacker to join a meeting as moderator using a join link that was originally created for viewer access. This vulnerability has been patched in version(s) 2.6.18, 2.7.8 and 3.0.0-alpha.7.
https://github.com/bigbluebutton/bigbluebutton/security/advisories/GHSA-4m48-49h7-f3c4
https://github.com/bigbluebutton/bigbluebutton/pull/20279
https://github.com/bigbluebutton/bigbluebutton/commit/ea6e9461dceae8fa593543d8c686f77bb8677e72
https://github.com/bigbluebutton/bigbluebutton/commit/a9d436accdcd26ea66bed9f391488ac128cd62d1