GHSA-c2j3-45gr-mqc4: DOMPurify: `CUSTOM_ELEMENT_HANDLING` bypasses `afterSanitizeElements` for allowed custom elements.

There is a possible hook-policy inconsistency in DOMPurify 3.4.11 involving CUSTOM_ELEMENT_HANDLING.

When a custom element is allowed via CUSTOM_ELEMENT_HANDLING.tagNameCheck, it appears that the element does not go through afterSanitizeElements in the same way as a normal element. As a result, an application that relies on afterSanitizeElements as a security policy layer to strip sensitive attributes from all elements may see those attributes removed from normal elements but preserved on allowed custom elements.

This does not appear to be a direct DOMPurify XSS or a case where DOMPurify directly allows executable payloads. The preserved value is still inert at sanitize time. The issue becomes relevant when the allowed custom element later re-injects that attribute value into an HTML sink such as innerHTML, creating a second-order XSS gadget.