Moodle Improper Input Validation Vulnerability - CVE-2011-4294
The error-message functionality in Moodle 1.9.x before 1.9.13 2.0.x before 2.0.4 and 2.1.x before 2.1.1 does not ensure that a continuation link refers to an http or https URL for the local Moodle instance which might allow attackers to trick users into visiting arbitrary web sites via unspecified vectors.