Wagtail is an open source content management system built on Django. Prior to 7.0.9, 7.3.4, 7.4.3, and 8.0rc2, Wagtail applies ETag conditional request processing to the document serve endpoint before document permission and filename checks complete. An unauthenticated attacker who knows a document ID and a candidate SHA1 hash can submit If-Match or If-None-Match and distinguish the response, revealing whether that hash is present in the document library. The issue does not expose document contents, filenames, other metadata, or information about hashes the attacker does not already know. This issue is fixed in versions 7.0.9, 7.3.4, 7.4.3, and 8.0rc2.