The TeX filter in Moodle 1.6 before 1.6.9+, 1.7 before 1.7.7+, 1.8 before 1.8.9, and 1.9 before 1.9.5 allows user-assisted attackers to read arbitrary files via an input command in a "$$" sequence, which causes LaTeX to include the contents of the file.
https://www.redhat.com/archives/fedora-package-announce/2009-April/msg00079.html
https://www.redhat.com/archives/fedora-package-announce/2009-April/msg00077.html
https://www.exploit-db.com/exploits/8297
http://www.securityfocus.com/bid/34278
http://www.securityfocus.com/archive/1/502231/100/0/threaded
http://www.debian.org/security/2009/dsa-1761
http://tracker.moodle.org/browse/MDL-18552
http://secunia.com/advisories/35570
http://secunia.com/advisories/34600
http://secunia.com/advisories/34557
http://secunia.com/advisories/34517
http://lists.opensuse.org/opensuse-security-announce/2009-04/msg00010.html