Mastodon before 3.3.2 and 3.4.x before 3.4.6 has incorrect access control because it does not compact incoming signed JSON-LD activities. (JSON-LD signing has been supported since version 1.6.0.)
{ "cpes": [ "cpe:2.3:a:joinmastodon:mastodon:*:*:*:*:*:*:*:*" ], "severity": "Critical" }