Potentially Dangerous Request.Path (:)

I just updated our website to .NET 4.0 and ever since then I'm getting the following exception.

"A potentially dangerous Request.Path value was detected from the client (:)."

The requ开发者_如何学Pythonest URL is: "https://OURDOMAIN:443/:/0"

This request is from many different IPs but the client app seems to always be IE 6.0-8.0.

Why do we keep getting requests for ":/0" and how can we stop this filling our event logs?

Update:

It turns out it was a bad javascript file that was creating the erroneous request. Now I just need to figure out what's going awry in the js file.

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The request has to be coming from somewhere.

Do you have an invalid link on your page pointing to it?
Maybe check your Routes in the Global.asax.cs file.