mdeploy.php in Moodle through 2.5.9, 2.6.x before 2.6.9, 2.7.x before 2.7.6, and 2.8.x before 2.8.4 allows remote authenticated users to bypass intended access restrictions and extract archives to arbitrary directories via a crafted dataroot value.
https://github.com/advisories/GHSA-cm4r-58pj-h2ph
https://moodle.org/mod/forum/discuss.php?d=307381
http://openwall.com/lists/oss-security/2015/03/16/1
http://git.moodle.org/gw?p=moodle.git&a=search&h=HEAD&st=commit&s=MDL-49087