After uploading corrupted webm file, thumbnail generation error is thrown and internals are displayed to user in mediawiki upload page i.e.
Error creating thumbnail: '/usr/bin/ffmpeg' -nostdin -threads 1 -ss 5 -y -i '/usr/share/mediawiki/images/3/30/Test.webm' -ss 3 -s 1920x1080 -f mjpeg -an -vframes 1 '/tmp/transform_235ff3c0b54e.jpg' 2>&1 wgMaxShellMemory: 307200 ffmpeg version 5.1.6-0+deb12u1 Copyright (c) 2000-2024 the FFmpeg developers built with gcc 12 (Debian 12.2.0-14) configuration: --prefix=/usr --extra-version=0+deb12u1 --toolchain=hardened [...]
even if error displaying is turned off with
display_errors Off
$wgShowExceptionDetails is not set (= default false)
Such internals should not be displayed in UI for users in production just logged to error log.
Checked in mediawiki 1.39 from Debian 12.