We recently implemented a new error page on our website which sends emails to the webmaster containing the most recent server exception. We are running a ASP.NET 4 application, and last night we got many emails that were all the same error:
A potentially dangerous Request.Path value was detected from the client (:).
These errors we have seen before, but the odd thing is the path that is being requested. It is always the path:
I have scoured the different pages and can find no anchor tag that appears to point to any link like this. Is this an issue with our application or something else? In other words, do we need to fix anything or just ignore these?
Also, this path was requested consistently, seemingly by the same users, and often was requested from multiple pages they visited. User-agents ranged from Firefox to IE7 and 8.
Have you done anything like this in your css: background-image:url(about:blank);
This shouldn’t generate a http request however so I suspect you might have maybe a ./about:blank in there instead.