Cross-site Scripting vulnerability with encoded payload in silverstripe/framework

Silverstripe framework is the PHP framework forming the base for the Silverstripe CMS. In affected versions a bad actor with access to edit content in the CMS could add send a specifically crafted encoded payload to the server, which could be used to inject a JavaScript payload on the front end of the site. The payload would be sanitised on the client-side, but server-side sanitisation doesn't catch it. The server-side sanitisation logic has been updated to sanitise against this type of attack in version 5.2.16. All users are advised to upgrade. There are no known workarounds for this vulnerability.