The KSES text cleaning filter in lib/weblib.php in Moodle before 1.8.13 and 1.9.x before 1.9.9 does not properly handle vbscript URIs, which allows remote authenticated users to conduct cross-site scripting (XSS) attacks via HTML input.
https://bugzilla.redhat.com/show_bug.cgi?id=605809
http://www.vupen.com/english/advisories/2010/1571
http://www.vupen.com/english/advisories/2010/1530
http://www.openwall.com/lists/oss-security/2010/06/21/2
http://tracker.moodle.org/browse/MDL-22042
http://secunia.com/advisories/40352
http://secunia.com/advisories/40248
http://moodle.org/mod/forum/discuss.php?d=152368
http://lists.opensuse.org/opensuse-security-announce/2010-08/msg00001.html
http://lists.fedoraproject.org/pipermail/package-announce/2010-June/043340.html
http://lists.fedoraproject.org/pipermail/package-announce/2010-June/043291.html
http://lists.fedoraproject.org/pipermail/package-announce/2010-June/043285.html
http://docs.moodle.org/en/Moodle_1.9.9_release_notes
http://docs.moodle.org/en/Moodle_1.8.13_release_notes
http://cvs.moodle.org/moodle/lib/weblib.php?r1=1.970.2.171&r2=1.970.2.172
http://cvs.moodle.org/moodle/lib/weblib.php?r1=1.812.2.114&r2=1.812.2.115