Microsoft Internet Explorer 8 through 11 mishandles HTML attributes in HTTP responses, which allows remote attackers to bypass a cross-site scripting (XSS) protection mechanism via unspecified vectors, aka "Internet Explorer XSS Filter Bypass Vulnerability."
https://euvd.enisa.europa.eu/vulnerability/EUVD-2015-6081
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2015/ms15-124