Certificate verification bypass through the HTTP/2 Alt-Svc header — Mozilla

Security researcher Muneaki Nishimura discovered a flaw in the Mozilla’s HTTP Alternative Services implementation. If an Alt-Svc header is specified in the HTTP/2 response, SSL certificate verification can be bypassed for the specified alternate server. As a result of this, warnings of invalid SSL certificates will not be displayed and an attacker could potentially impersonate another site through a man-in-the-middle (MTIM), replacing the original certificate with their own.