Steps to reproduce:

1. Create a page with "&" in the title, like "you & me" (in the URL, it's "you_%26_me")
2. Delete that page
3. Go to Special:Undelete/you & me
4. Click on the link to the deleted revision.
5. No deleted revision is shown, instead the deletion log.

Expected behaviour:
Show deleted revision.

The Link is broken:
Special:Undelete&target=you_%2526_me&timestamp=....

The correct link is:
Special:Undelete&target=you+%26+me&timestamp=...

Note that "+" vs. "_" doesn't matter. It the "%2526" as opposed to "%26" part that breaks the link.

Version: unspecified
Severity: normal