We have an MFC app that embeds the WebBrowser ActiveX control. We use
custom URLs to send commands to the C++/MFC implementation class of the
browser control, which we handle in a method for the BeforeNavigate2
event, and Cancel the navigation.

The problem is that starting with IE7, URLs are being URL Escaped before
the call to the event handler. In particular, the '{' and '}'
characters are being changed to '%7B' and '%7D'. This didn't happen
with IE5 through 6. This is breaking our applications in the field.

Obviously the C++ code can be modified to handle this, but it leaves two
problems:
1) Existing user installations continue to fail.
2) Will the behaviour change in the future, and thus break the work-around?

Is there anything I can do? I can modify the code to unescape the URL,
but that's a bit of a headache as it could affect every URL, or I need
to do it on a case-by-case basis and hope I or QA catches all of the
situations.

Is this a bug in IE7?