If your site runs on MODx Revolution, we have bad news for you. Developers have discovered (and already fixed) two critical vulnerabilities in it: the first allows a site to be wiped with a single request, the second allows uploading an arbitrary file (including a PHP script) and remote code execution (RCE).
https://modx.com/blog/modx-revolution-2.6.5
All versions up to and including 2.6.4 are affected. We recommend urgently updating the CMS to 2.6.5.