DOMPurify versions prior to 3.4.13 contain a vulnerability in the IN_PLACE sanitization mode where a hook that removes an element can leave detached descendant elements executable. This allows an attacker who can supply HTML to execute JavaScript via retained event handlers on detached subtrees after sanitization completes. The issue arises because the sanitization process skips neutralizing the subtree of a detached node when a hook removes it, leaving event handlers intact on disconnected elements.