src/net/http/http_transaction_winhttp.cc in Google Chrome before 1.0.154.53 uses the HTTP Host header to determine the context of a document provided in a (1) 4xx or (2) 5xx CONNECT response from a proxy server, which allows man-in-the-middle attackers to execute arbitrary web script by modifying this CONNECT response, aka an "SSL tampering" attack.
https://exchange.xforce.ibmcloud.com/vulnerabilities/51194
https://bugzilla.mozilla.org/show_bug.cgi?id=479880
http://src.chromium.org/viewvc/chrome?view=rev&revision=11669
http://research.microsoft.com/pubs/79323/pbp-final-with-update.pdf
http://research.microsoft.com/apps/pubs/default.aspx?id=79323