WordPress MU is prone to multiple cross-site scripting vulnerabilities because it fails to sufficiently sanitize user-supplied data. An attacker may leverage these issues to execute arbitrary script code in the browser of an unsuspecting user in the context of the affected site. This may allow the attacker to steal cookie-based authentication credentials and to launch other attacks. WordPress MU versions prior to 2.6 are vulnerable.
Update to WordPress MU version 2.6 or latest
WordPress Plugin Exit Popup Show Cross-Site Scripting (1.0)
WordPress 3.9.x Cross-Site Request Forgery (3.9 - 3.9.26)
WordPress Plugin Advanced Booking Calendar Cross-Site Scripting (1.6.7)
WordPress Plugin Page and Post Clone Information Disclosure (1.1)
WordPress Plugin Advanced Woo Search Information Disclosure (1.99)