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Moodle Cross Site Scripting Vulnerability (post.php)
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SUMMARY
" <http://www.moodle.org> Moodle is a course management system (CMS) - a
software package designed to help educators create quality online
courses."
Moodle suffers from a cross-site scripting vulnerability due to handling
of user supplied parameters in an unsafe manner.
DETAILS
Vulnerable Systems:
* Moodle versions 1.3 and prior
Immune Systems:
* Moodle version 1.3.3
The cross-site scripting (XSS) vulnerability is caused by un-filtering the
$reply variable. Here is an excerpt from the original code:
/* Begin of vulnerable code */
} else if (isset($reply)) { // User is writing a new reply
if (! $parent = forum_get_post_full($reply)) {
error("Parent post ID was incorrect ($reply)");
}
if (! $discussion = get_record("forum_discussions", "id",
$parent->discussion)) {
error("This post is not part of a discussion! ($reply)");
}
if (! $forum = get_record("forum", "id", $discussion->forum)) {
error("The forum number was incorrect ($discussion->forum)");
}
if (! $course = get_record("course", "id", $discussion->course)) {
error("The course number was incorrect ($discussion->course)");
}
if (! forum_user_can_post($forum)) {
error("Sorry, but you can not post in this forum.");
}
if ($cm = get_coursemodule_from_instance("forum", $forum->id,
$course->id)) {
if (groupmode($course, $cm) and !isteacheredit($course->id)) { //
Make sure user can post here
if (mygroupid($course->id) != $discussion->groupid) {
error("Sorry, but you can not post in this discussion.");
}
}
if (!$cm->visible and !isteacher($course->id)) {
error(get_string("activityiscurrentlyhidden"));
}
}
/* End of vulnerable code */
The bug can be specifically traced to the following snippet of code:
if (! $parent = forum_get_post_full($reply)) {
error("Parent post ID was incorrect ($reply)");
A proof of concept HTTP request that will pop up an alert dialog in the
victim's context:
http://www.vulnerable.com/moodle/mod/forum/post.php?reply=%3Cscript%3Ealert(document.cookie);%3C/script%3E
Vendor Status:
The vendor has been contacted and a new version is available for download.
ADDITIONAL INFORMATION
The information has been provided by <mailto:javierubilla@spymac.com>
Javier Ubilla Brenni.
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