Tiptap for PHP before version 2.1.1 contains an input validation vulnerability that allows authenticated attackers to cause a denial of service by submitting Tiptap JSON with the attrs.href field set to an array instead of a string, causing an unhandled TypeError in the Link::isAllowedUri() function when passed to preg_match(). Attackers can persist malformed JSON records that permanently crash the server-side HTML rendering pipeline for all subsequent viewers of that record until the database entry is manually repaired.