Apparently, the contents of all 2016 versions of the File description page have been lost in the Commons MW database, this looks like data corruption in the Commons DB. If so, there are probably other losses (possibly caused by the ongoing massive spam on Commons, and an unexpected manual data purge with wrong page ids by some SQL admins or caused by the attack itself: it's more than spammers then.)
May be the security team could be involved to investigate what happened in these recent days of attacks.
Can those missing versions be restored, or do we have to restore an old 2015 version (possibly missing the 2016 edits) of the description page ?

I've tried restoring the last 2015 version (working) of the description page. Now I see that the 2016 versions are still in the database, and I can see its internal code. The main difference is that in 2016 it used [[c:Template:Infobox flag]] which internally used some Lua module. I suspect an infinite loop in some Lua module, causing the MW page renderer to halt.

So the bug is not really in the image server.

However, except if we are not looking at the file description page, this should not block the image server that should render image thumbnails, including for other wikis: it should not report to other wikis that the file as non-existing.

I don't think its related to the actual image.

Error seems to be about image description

"/srv/mediawiki/php-1.28.0-wmf.11/includes/parser/StripState.php\\\",\\\"line\\\":82,\\\"message\\\":\\\"Invalid marker: '\\\\\\\"UNIQ--<span class=\\\\\\\"error\\\\\\\">Expansion depth limit exceeded</span>-00000001-QINU\\\\\\\"'\\

Example page https://commons.wikimedia.org/w/index.php?title=File:Flag_of_Germany.svg&oldid=192017176

Backtrace of V5JYMApAMFIAALoducMAAAAA indicates Scribunto as the offender (and I can't think of any other way to produce such broken strip markers). (I'd paste the backtrace here but logstash no longer has them in a sane format.)

This has nothing to do with Scribunto. Any wikitext where the expansion depth exceeded happens to occur inside the expansion that's involved in the generation of a strip marker causes it.

But why Scribunto is involved in sharing images or thumbnails from other wikis ?
They just request the image, it should not be reported as "not existing" and other wikis should not behave as if the image did not exist, they are actually NOT using the description page itself, they just request the image in some sizes (generally they request only a thumbnail).
Why does the image server requires parsing the file description page???

So may be there's a bug in Scribunto, but there's also a bug in the image server if it has such "stupid" dependency with the image description page which is not even requested (unless such sharing is only permitted if the image does not belong to some tracking category, generated by wikicode in the description page;

• my opinion is if such permission is needed it should not be part of the wikicode of the page description but within some metadata stored separately and not requiring parsing the file description page itself.
• if this is needed to detect redirected file description pages, it is also known that files cannot be renamed, except by administrative tools, not altering the file descriotion page. Redirecting a file description page to another page by wiki editing should not affect the file itself, and in fact it should not even work as long as files themselves cannot be moved at the same time.

The language is not relevant. To solve the problem for now I have replaced
the last 2016 version of the description page by the last version of 2015
which did not cause that problem (occuring because it was changed in 2016
to use another template using a Lua module which is now broken).
You can still see the problem by looking at 2016 versions just before the
one I wrote: look into the page history.
There was no change in the SVG image data itself (not changed since 2007).

In T141132#2488762, @matmarex wrote:

(I'd paste the backtrace here but logstash no longer has them in a sane format.)