MyBB 1.8.6 Username cross site scripting

Summaryinfo

A vulnerability classified as problematic was found in MyBB 1.8.6. The impacted element is an unknown function of the component Username Handler. Executing a manipulation can lead to cross site scripting. The attack can be launched remotely. Moreover, an exploit is present. Upgrading the affected component is advised.

Detailsinfo

A vulnerability was found in MyBB 1.8.6 (Content Management System). It has been declared as problematic. This vulnerability affects an unknown function of the component Username Handler. The manipulation with an unknown input leads to a cross site scripting vulnerability. The CWE definition for the vulnerability is CWE-80. The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes special characters such as "<", ">", and "&" that could be interpreted as web-scripting elements when they are sent to a downstream component that processes web pages. As an impact it is known to affect integrity.

The weakness was disclosed 11/10/2016 by Tim Coen with Curesec Research Team as MyBB 1.8.6: XSS as not defined mailinglist post (Full-Disclosure). The advisory is available at seclists.org. The public release has been coordinated in cooperation with the vendor. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. Successful exploitation requires user interaction by the victim. Technical details are unknown but a public exploit is available. This vulnerability is assigned to T1059.007 by the MITRE ATT&CK project. The advisory points out:

The username is echoed unencoded in the user area. As the login does not have CSRF protection and as an admin can be logged into the admin area with a different account than the one they are logged into the forum, a persistent XSS vulnerability in the user area can be exploited. However, successful exploitation most likely requires a username length of at least 43 characters, which is more than the default settings allow.

A public exploit has been developed by Tim Coen and been published immediately after the advisory. It is possible to download the exploit at seclists.org. It is declared as proof-of-concept. The vulnerability was handled as a non-public zero-day exploit for at least 279 days. During that time the estimated underground price was around $5k-$25k.

Upgrading to version 1.8.7 eliminates this vulnerability. The upgrade is hosted for download at resources.mybb.com. A possible mitigation has been published before and not just after the disclosure of the vulnerability.

The entries VDB-93560, VDB-93561, VDB-93563 and VDB-93564 are pretty similar. If you want to get best quality of vulnerability data, you may have to visit VulDB.

Productinfo

Type

• Content Management System

Name

• MyBB

Version

• 1.8.6

License

• open-source

Website

• Product: https://mybb.com/

CPE 2.3info

• 🔍

CPE 2.2info

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If you want to get best quality of vulnerability data, you may have to visit VulDB.

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