Today, we are releasing XenForo 2.1.9 to address a potential security vulnerability that may affect any customer who makes use of our PayPal payment handler.
As well as user upgrades, this may affect add-ons you have installed which process payments using our PayPal payment handler.
We recommend that all affected customers running XenForo 2.1 upgrade to 2.1.9 or use one of the attached patch files as soon as possible.
