Many projects have noticeboards that allow searching through the archives. These have worked in the past by appending "prefix:<whatever noticeboard>" to the search term requested.
This no longer works in enwiki or commons, it returns zero results but gives the following error:
A warning has occured while searching: The namespace found in the search term prefix: is not compatible with the namespaces requested. You can fix it by prefixing your query with all:.
This occurs both logged in with Monobook and logged out with whatever the default is these days, on both Chrome and Firefox.
Sample searches that should return results: