User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; cs; rv:1.9.0.10) Gecko/2009042316 Firefox/3.0.10 (.NET CLR 3.5.30729) Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; cs; rv:1.9.0.10) Gecko/2009042316 Firefox/3.0.10 (.NET CLR 3.5.30729) Firefox can correctly detect if HTTPS page gets blocked by proxy server. Typing https://blockedsite into address bar doesnt hangs him. But if request to blocked https site is from <script tag> FF networking hangs in (Transfering data from on statusbar) and cant even detect that proxy server closed TCP connection after timeout. Response from proxy server is following: -> CONNECT ad.doubleclick.net:443 HTTP/1.1 -< HTTP/1.0 403 OK -< Content-type: text/html -< Content-length: 337 -< Proxy-Connection: Keep-alive [... html formated error message from proxy ...] offending part of JS: <!-- DoubleClick Random Number --> <script language="JavaScript" type="text/javascript"> dfp_ord=Math.random()*10000000000000000; dfp_tile = 1; </script> <script type="text/javascript"> //<![CDATA[ document.write('<script src="https://ad.doubleclick.net/adj/ostg.sourceforge/project_web_p85_skybox;pg=default;dcopt=ist;tile='+dfp_tile+'; tpc={SFN-APPNAME};tpc=scache;ord='+dfp_ord+'?" type="text/javascript"><\/script>'); dfp_tile++; //]]> </script> Reproducible: Always Steps to Reproduce: 1. Get HTTPS proxy server with URL Filtering. I am using scache.sf.net but others (Squid) should work too. 2. block URL with string *ad.doubleclick.net* 3. test on mantis bug tracker on sf.net https://apps.sourceforge.net/mantisbt/scache/roadmap_page.php FF 3.0.10 Smart Cache revision 104 from Bazaar repo http://scache.bzr.sourceforge.net/bzr/scache/head/files

This seems to be the same issue as: https://bugzilla.mozilla.org/show_bug.cgi?id=492459

Here is dump of Smart Cache console to see what FF is doing: [TRACE Thread-33] > CONNECT data.coremetrics.com:443 HTTP/1.1 [TRACE Thread-34] > CONNECT ad.doubleclick.net:443 HTTP/1.1 [TRACE Thread-34] ! Blocked https://ad.doubleclick.net:443/ by ^https?://ads?[0-9]*\. [TRACE Thread-34] = Waiting for next request on connection. [1 minute later - input connection timeout] [TRACE Thread-34] = Input connection timed out. Last message on status bar is Transfering data from data.coremetrics.com. After input connection timeout Smart Cache closed keep-alive proxy input connection but FF was still hanging.