I have been having intermittent app pool crashes on an iis 6 website. I have identified the requests that are causing this are coming from Googlebot, the request is as follows (taken from the httperr log)

HTTP/1.1 GET /Folder/PageName.html?iframe=true&width=95%&height=95%

The page being requested changes but the Querystring is consistent.

I have tried adding code to global.asax.cs to strip these invalid querystrings, but it seems the querystring causes 'Connection_Abandoned_By_AppPool' before hitting my code.

Clearly I need to handle this earlier, but I am really not sure where ??

  • I have just read that a Plesk ISAPI filter urlprotect.dll is the cause of the issue. Documented in this forum: forum.parallels.com/showthread.php?t=83376 - it unfortunately does not offer a working solution, but sheds more light, learning... – Alan Aug 1 '12 at 0:38

The percent symbol is a special character in URLs.. you need to encode it. to "%25"


Continuing my research I found that Parallels Plesk 8.6 software that my webserver uses includes a ISAPI filter called urlprotect.dll which essentially just allows certain URLs on a site to be password protected.

This ISAPI filter is applied (in this version of Plesk at least) to all websites on the server by default, even if you do not define any protected URLs.

This is the cause of the failure to handle unescaped percent signs in URLs.

I found this information at this forum post (http://forum.parallels.com/showthread.php?t=83376) which also indicates that there has been no successful resolution to the dll's issue.

If you do not need to protect any URL's in this way then my experience is that it can be safely removed from the site(s) through IIS without any ill effects.

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