Plugin downloads are re-verified as they move into the cache, and a failed move cleans up after itself.
What's wrong with this entry?
Moving a downloaded plugin into the version cache now re-verifies the destination before, during and after the move under an internal strict-cache mode, refuses a path whose current occupant cannot be examined, and deletes the staged copy if the move throws. The permissive rename and copy helpers it replaces were removed.
plugin cache version path occupant could not be examined
Strings lifted out of the shipped bundle, so the claim above can be checked against them.