Package contains a .thumbnails directory. It was most likely installed by accident, since thumbnails usually don't belong in packages.
For more information please consult:
The tag is present in Lintian version
That is the most recent version we know about.
We use semantic versions.
The patch number is a commit step indicator relative to the
release tag in our Git
You can find the detection logic for this version at commit 3410a22. For merge requests, please use the latest version in the Lintian check images/thumbnails.