Hmm, Extension:Vector is installed in your wiki.
The only potentially relevant items that I can find in https://gerrit.wikimedia.org/r/gitweb?p=mediawiki/extensions/Vector.git;a=shortlog is bug 42354.

First: Confirmation that the problem occurs under Windows Chrome/FF as well.

Second: our copy of the Vector extension is from git-Head, so the bugfix
https://gerrit.wikimedia.org/r/#/q/status:merged+project:mediawiki/extensions/Vector,n,z should be included.

Third: we just discussed this and will try to disable selected extensions (the set of extensions worked ok under 1.18.x, but there may be some possible interference with changes in 1.20).

Might be related: Similar problem described at https://de.wikipedia.org/wiki/Wikipedia:FZW#Sidebar_f.C3.BCr_unangemeldete_Benutzer_defekt.3F for users that are not logged-in.

Looks like a regression from bug 42452 comment 37

The actual headings in the sidebar menu of version 1.20.2 are h5, ext.vector.collapsibleNav.css supports both h3 and h5 to be backwards compatible, but on cursory review it seems to me that ext.vector.collapsibleNav.js supports only h3, see e.g. or current version of HEAD (WMF may be different). https://gerrit.wikimedia.org/r/#/c/34702/2/modules/ext.vector.collapsibleNav.js

To me this seems to be a valid bug and no strange interaction with other extensions.

Also mentioned in https://de.wikipedia.org/w/index.php?title=Wikipedia:Fragen_zur_Wikipedia&oldid=111927103#Sidebar_f.C3.BCr_unangemeldete_Benutzer_defekt.3F

I submitted I0a05ed39 to clean it up.

Good! I0a05ed39 is submitted to master but how can it be included into the mediawiki version 1.20.2?

Hi Andreas,

(In reply to comment #8)

Good! I0a05ed39 is submitted to master

It says "Status: Review in Progress" - it's not merged yet.

but how can it be included into the mediawiki version 1.20.2?

Are you asking how to apply the patch manually to your installation, or do you ask for a time machine to go back & put this in before 1.20.2 was released? :)

Dear André

Are you asking how to apply the patch manually to your installation, or do you
ask for a time machine to go back & put this in before 1.20.2 was released? :)

time machine would be nice ;-)

I'm uncertain how it will be merged or be managed: MW 1.20.2 with vector extension has this bug and if it will be corrected, will there be an update/bug-fix release to MW 1.20.2 or do I have to use another MW 1.20.X or MW 1.2X version? On our Wiki we use presently MW core 1.20.2.

I guess I'll have to wait.

Andreas

This patch is for the Vector extension anyway, not for MediaWiki core. So you would have to update Vector.

You can get the patch for this change using the command provided in the "Download -> patch" section on gerrit. Then you can apply it in the usual way.

I have manually applied the code and can confirm that it will be working.

Please do a code review however and accept it in master. At the moment anyone trying to install mediawiki 1.20.2 will run against a wall here (yes, Vector is formally an extension, but there will be hardly a mediawiki installation that uses the vector skin (= new installation default), but does not use the standard functionality that only the extension provides).

Merged, thanks to all who helped out.

(Making a release with the fixed version etc will probably be handled at bug 42452.)

(In reply to comment #12)

Please do a code review however and accept it in master. At the moment anyone
trying to install mediawiki 1.20.2 will run against a wall here (yes, Vector
is
formally an extension, but there will be hardly a mediawiki installation that
uses the vector skin (= new installation default), but does not use the
standard functionality that only the extension provides).

This accessibility fix (h5 -> h3) was merged in master with I9a2ebd50.
This caused a bug in extensions/Vector which was fixed in these:

• I0a05ed39
• I7a20e853
• Id4a2058f
• I64794145

Neither are part of 1.20, so there is nothing to backport.

My mistake; I misread the comments here.

The bug only manifested on a combination of MW core 1.20.2 or older with the Vector extension versions I64794145, Id4a2058f, I7a20e853 (the three linked by Krinkle).

Both current git master of Vector and a version older than I0a05ed39 (such as the one bundled with 1.20.2 release) work okay.

Yes, everything is ok now. When I wrote "Please do a code review however and accept it in master" I did not mean core, but vector; at the time of writing the fix by Bartosz (thanks Bartosz!) was not included when checking out extension/Vector HEAD.