Apache Httpd < 2.4.41 : Limited cross-site scripting in mod_proxy error page

A limited cross-site scripting issue was reported affecting the mod_proxy error page. An attacker could cause the link on the error page to be malfomed and instead point to a page of their choice. This would only be exploitable where a server was set up with proxying enabled but was misconfigured in such a way that the Proxy Error page was displayed. We have taken this opportunity to also remove request data from many other in-built error messages. Note however this issue did not affect them directly and their output was already escaped to prevent cross-site scripting attacks.