Design/Logic Flaw

In Symfony before versions 4.4.7 and 5.0.7, when a Response does not contain a Content-Type header, affected versions of Symfony can fallback to the format defined in the Accept header of the request, leading to a possible mismatch between the response's content and Content-Type header. When the response is cached, this can prevent the use of the website by other users. This has been patched in versions 4.4.7 and 5.0.7.