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`:

```wikitext {{#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.