In PHP before 5.6.28 and 7.x before 7.0.13, incorrect handling of various URI components in the URL parser could be used by attackers to bypass hostname-specific URL checks, as demonstrated by evil.example.com:80#@good.example.com/ and evil.example.com:80?@good.example.com/ inputs to the parse_url function (implemented in the php_url_parse_ex function in ext/standard/url.c).