Report at https://www.mediawiki.org/wiki/Topic:Scb851zpf3p2i230
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If we use Hovercards for the link to "Citizenfour" at https://de.wikipedia.org/wiki/Oscarverleihung_2015#Bester_Dokumentarfilm
it shows a pure black image
{F83276}
The first frame of the video is indeed black,
But the wikitext at https://de.wikipedia.org/wiki/Citizenfour_(Film) is:
`[[Datei:CITIZENFOUR (2014) trailer.webm|miniatur|thumbtime=1:05|Film-Trailer ''Citizenfour'']]`
which shows a nice preview thumbnail
{F83281}
If possible (?), it would be good if PageImages could detect the use of `thumbtime=`
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Sidenote: I had difficulty reproducing this bug, at metawiki, where I added the video to my sandbox:
https://meta.wikimedia.org/w/index.php?title=User:Quiddity_%28WMF%29/sandbox&oldid=11525812 (current content, might change)
but the Hovercard for the link there (at my userpage), only shows the text content - no image at all.
== Acceptance criteria
[] Blacklist webm files from PageImages extension
== Developer notes
There are 2 possible ways to do this. Inside LinksUpdateHookHandler::getUrlBlacklist or operating on LinksUpdateHookHandler::fetchFileMetadata
== Signoff criteria
[] Update changes in functionality in https://www.mediawiki.org/wiki/Beta_Features/Hovercards (Olga)