CVE-2023-42451
Mastodon is a free, open-source social network server based on ActivityPub. Prior to versions 3.5.14, 4.0.10, 4.1.8, and 4.2.0-rc2, under certain circumstances, attackers can exploit a flaw in domain name normalization to spoof domains they do not own. Versions 3.5.14, 4.0.10, 4.1.8, and 4.2.0-rc2 contain a patch for this issue.
Source: CVE-2023-42451