When using the Advanced tab in Special:Search the "Search in namespaces:" section only shows the namespaces which had been protected through Extension:Lockdown (i.e.namespaces included in $wgNamespacePermissionLockdown variable).
The bug was observable for users with permissions granted for these lockdown namespaces as well as anonymous users.
- Tested on: MediaWiki v1.28.2 (438c3d6) - 00:03, 1 May 2017
- On extension branches: master, REL1_29, REL1_28
Fortunately, the problem does not exist for REL1_27.
On further investigation with individual commits for finding out which commit caused the breaking changes used the Rel1_28 commit history.
Special:Search works fine up-to-the commit, Merge "The parameter to the SearchableNamespaces hook handler needs to be a…
git checkout b19a0a60a476ddbf5344395b339e928729c11f54
For whatever reason, the Special:Search bug appears in the very next commit, Consolidate hook handler code
git checkout 6ef74a58be6ee453452470f274a76b5fc5fa211b