This should be possible with urllib.
path = urllib.unquote(data)
path = urllib.unquote_plus(data)
But actually this should be seen as a bug of the webserver plugin. Of course it should do it itself before initiating the event. I will look into it later.
You shouldn't use the event to transfer data. The event.payload is meant for such purposes. Make the URL by putting the pieces together with the "&" sign, like:http://localhost/index.html?myEvent&C
(with right encoding it should actually look like:http://localhost/index.html?myEvent&C%3A%5Cwhatever%5C
and you get always the event "myEvent" and the path as eg.event.payload
Please post software-related questions in the forum - PMs will only be answered, if really private, thanks!