An issue was discovered in inc/class_feedgeneration.php in MyBB 1.8.17. On the forum RSS Syndication page, one can generate a URL such as http://localhost/syndication.php?fid=&type=atom1.0&limit=15. The thread titles (within title elements of the generated XML documents) aren't sanitized, leading to XSS.
SQL injection vulnerability in userbarsettings.php in the Userbar plugin 2.2 for MyBB Forum allows remote attackers to execute arbitrary SQL commands via the image2 parameter.
SQL injection vulnerability in pages.php in Custom Pages 1.0 plugin for MyBulletinBoard (MyBB) allows remote attackers to execute arbitrary SQL commands via the page parameter.