GHSA-7pgw-q3qp-6pgq

Summary

Several #dpl parameters can leak usernames that have been hidden using revision deletion, suppression, or the hideuser block flag.

Details

The parameters adduser, addauthor, and addlasteditor output the page creator or last editor using the %USER% placeholder. These display the actual username, even when that name has been hidden using revision deletion, suppression (oversight), or hideuser.

The %CONTRIBUTOR% placeholder, used with addcontribution, behaves similarly and also reveals hidden usernames.

In addition, the following parameters can expose suppressed usernames when combined with %USER% or similar output placeholders: - lastrevisionbefore - allrevisionsbefore - firstrevisionsince - allrevisionssince

These parameters reference specific revisions and allow output of user-related metadata. If a username has been hidden from those revisions, it may still appear in the output.

Further, the parameters createdby, notcreatedby, modifiedby, notmodifiedby, lastmodifiedby, and notlastmodifiedby accept usernames as input. When the correct (suppressed) username is used, the query may return matching pages or edits. This can reveal the presence and association of a hidden identity, even if not displayed directly. However, this is a more indirect exposure than the output parameters mentioned above.

Proof of Concept

1. Create a page while logged in as a user.
2. Revision delete or suppress the username from the page history.
3. Use a DPL query with one of the affected parameters.
4. The output reveals the hidden username.

Example

The following query reveals the suppressed username Example user:

{{#dpl:
| title = File:Example.png
| addauthor = true
| format = ,%USER%,,
}}

Similar behavior occurs using parameters like lastrevisionbefore with %USER% in the format string.

Impact

This issue causes the exposure of usernames that were intentionally hidden by administrators. It directly undermines revision deletion, user suppression, and block-related privacy measures. In some cases, usernames can be revealed both directly through output and indirectly through query behavior.