Atutor 2.2: XSS

Date: 2016-02-01 10:09:39

1. Introduction

2. Overview

Atutor is a learning management system (LMS) written in PHP. In version 2.2, it is vulnerable to multiple reflected and persistent XSS attacks.

The vulnerabilities can lead to the stealing of cookies, injection of keyloggers, or the bypassing of CSRF protection. If the victim is an admin, a successful exploitation can lead to code execution via the theme uploader, and if the victim is an instructor, this can lead to code execution via a file upload vulnerability in the same version of Atutor.

3. Details

XSS 1: Reflected XSS - Calendar

CVSS: Medium 4.3 AV:N/AC:M/Au:N/C:N/I:P/A:N

Description: The calendar_next parameter of the calendar is vulnerable to XSS. This issue has been fixed in ATutor 2.2.1-RC1.

Proof of Concept:

http://localhost/ATutor/mods/_standard/calendar/getlanguage.php?token=calendar_next<script>alert(1)<%2fscript>&pub=1

Code:

/mods/_standard/calendar/getlanguage.php $token = $_GET['token']; echo _AT($token);

XSS 2: Persistent XSS - Profile

CVSS: Medium 5.0 AV:N/AC:L/Au:N/C:N/I:P/A:N

Description: When saving profile information, < is filtered out. &lt; on the other hand is not filtered, but converted to <, which leads to persistent XSS.

A user account is needed, but registration is open by default. This issue has been fixed in ATutor 2.2.1.

Proof of Concept:

Visit: http://localhost/ATutor/users/profile.php In any field, enter &lt;img src=no onerror=alert(1)>

The input is for example echoed when visiting http://localhost/ATutor/users/profile.php. This self-XSS may be exploited by force-logging in the victim.

The input is not only echoed to the user themselves, but also in other places. For example, an attacker could send a private message to a victim. When the victim views the message, or visits their inbox, the injected code will be executed.

XSS 3: Persistent XSS - Forum

CVSS: Medium 5.0 AV:N/AC:L/Au:N/C:N/I:P/A:N

Description: When creating a forum post, the Subject parameter is vulnerable to persistent XSS.

A user account is needed, but registration is open by default. This issue has been fixed in ATutor 2.2.1.

Proof of Concept:

Visit a forum, eg here: http://localhost/ATutor/mods/_standard/forums/forum/view.php?fid=1&pid=1 Post a new message, as Subject, use: Re: test topic'"><img src=no onerror=alert(1)>

In ATutor 2.2.1-RC1, < and > are encoded, preventing the proof of concept from working. But until version 2.2.1, it was still possible to exploit this issue either by using the JavaScript context the input is echoed into (onClick), or by adding a new attribute:

adding new attributes: Re: ';" onmouseover="alert(1); var foo=' staying inside the existing JavaScript context: Re: test topic';alert(1);var foo='

XSS 4: Persistent self-XSS - Calendar

CVSS: Low 2.6 AV:N/AC:H/Au:N/C:N/I:P/A:N

Description: The event name of the calendar is vulnerable to persistent XSS. The calendar seems to be shown only to the user creating it, meaning the only way to exploit this issue would be to force-login the victim.

A user account is needed, but registration is open by default. This issue has been fixed in ATutor 2.2.1-RC1.

Proof of Concept:

Visit: http://localhost/ATutor/mods/_standard/calendar/index_mystart.php Create event with name: '"><img src=no onerror=alert(1)> Visit event page: http://localhost/ATutor/mods/_standard/calendar/index_mystart.php

XSS 5: Persistent XSS - Chat

CVSS: Medium 5.0 AV:N/AC:L/Au:N/C:N/I:P/A:N

Description: When viewing the chat history, chat messages are not properly HTML encoded, leading to persistent XSS.

A user account is needed, but registration is open by default. This issue has been fixed in ATutor 2.2.1-RC1.

Proof of Concept:

1. Visit Chat: http://localhost/ATutor/mods/_standard/chat/chat.php 2. Enter chat message: '"><img src=no onerror=alert(1)> 3. Visit chat history of that user: http://localhost/ATutor/mods/_standard/chat/filterHistory.php?filterChatID=[USERNAME]

4. Solution

To mitigate this issue please upgrade at least to version 2.2.1:

http://www.atutor.ca/atutor/download.php

Please note that a newer version might already be available.

5. Report Timeline