The remote host is missing an update to moodle announced via advisory USN-791-2.
Details follow:
Christian Eibl discovered that the TeX filter in Moodle allowed any function to be used. An authenticated remote attacker could post a specially crafted TeX formula to execute arbitrary TeX functions, potentially reading any file accessible to the web server user, leading to a loss of privacy. (CVE-2009-1171, MSA-09-0009)
Solution: The problem can be corrected by upgrading your system to the following package versions:
Ubuntu 9.04: moodle 1.9.4.dfsg-0ubuntu1.1
After a standard system upgrade you need to access the Moodle instance and accept the database update to clear any invalid cached data.