DRUPAL-CONTRIB-2026-165

The Webform module allows site builders to create forms, collect submissions, and configure access to forms and submission data. When Webform is used with JSON:API enabled, submissions may be cached without varying correctly by the authenticated user. If a webform is configured so that authenticated users can view their own submissions, a request to the JSON:API webform submission collection can return a cached response generated for a different user. This can allow an authenticated user to view another user's webform submission data through the JSON:API collection endpoint. This vulnerability is mitigated by the fact that JSON:API must be enabled, the affected webform must expose submissions through JSON:API, and the attacker must have an account with permission to view their own submissions for the affected webform.