UBUNTU-CVE-2016-4554

mimeheader.cc in Squid before 3.5.18 allows remote attackers to bypass intended same-origin restrictions and possibly conduct cache-poisoning attacks via a crafted HTTP Host header, aka a "header smuggling" issue...

security flaw

Firefox before 1.0.7 and Mozilla Suite before 1.7.12 allows remote attackers to modify HTTP headers of XML HTTP requests via XMLHttpRequest, and possibly use the client to exploit vulnerabilities in servers or proxies, including HTTP request smuggling and HTTP request splitting...