Certain buggy HTTP servers expect two extra bytes, CR and LF characters, following an HTTP POST message body. It seems unlikely that such uncompliant servers are still in use today. Nonetheless, this access rule list exists to accommodate them. When a request matches a broken_posts rule, Squid appends the extra CRLF characters.
broken_posts allow|deny [!]
acl NeedsExtraCRLF dstdomain broken.server.com broken_posts allow NeedsExtraCRLF