The bug happening on 1.20wmf1 on mediawiki.org
When I initially fixed[1] SyntaxHighlighter a few months back to use <pre class="mw-geshi>...geshi output</pre> instead of <div class="mw-geshi>...geshi output</div>
( .. so that PRE styles by skins apply to geshi, without requiring local wikis to maintain a copy of each skins's <pre> css style and apply it in MediaWiki:Common.css to div.mw-geshi) .. )
.. it was working fine on SVN trunk. Then I requested that fix to be merged to 1.19wmf1 then suddenly this bug was occurring, the same bug that is happening now. Back then I figured it was due to a change in 1.20 that therefor didn't work well on 1.19wmf1 so it[2] was backed out[3].
But now that 1.20wmf1 is live I'm seeing the same bug again (see attachment).
Oddly enough it still isn't happening on my localhost running git master (2nd attachment), so contrary to what I suspected a few months back it can't be due to changes in core since the branching because 1.20wmf1 was branched *today*. It has to be something specific to wmf config.
Version: unspecified
Severity: blocker
URL: https://www.mediawiki.org/w/index.php?title=Project:Sandbox&oldid=523532
Attached: