Stronger revision number limitations were required on file serving endpoints to improve cache poisoning protection.
https://moodle.org/mod/forum/discuss.php?d=451589
https://bugzilla.redhat.com/show_bug.cgi?id=2243449
http://git.moodle.org/gw?p=moodle.git&a=search&h=HEAD&st=commit&s=MDL-77846