Moodle is vulnerable to remote code execution (RCE). A malicious user can use the portfolio API callback to upload and execute malicious files.
git.moodle.org/gw?p=moodle.git&a=search&h=HEAD&st=commit&s=MDL-33791
git.moodle.org/gw?p=moodle.git&a=search&h=HEAD&st=commit&s=MDL-36346
openwall.com/lists/oss-security/2012/11/19/1
www.securityfocus.com/bid/56505
git.moodle.org/gw?p=moodle.git&a=search&h=HEAD&st=commit&s=MDL-33791
moodle.org/mod/forum/discuss.php?d=216159