If you have ever had to debug HTTP traffic, you probably already know what a great tool Fiddler2 is. I was recently using it to debug some WordPress 2.5 issues I was having with a test blog and noticed I was getting an odd error returned from the web site: Error 403
I recognized this as the error that Bad Behavior (a spam-fighting plugin) returns when it sees something wrong with the the request being made to the web site. Apparently Fiddler was sending a “Proxy-Connection: Keep-Alive” header that Bad Behavior was rejecting as invalid. I thought that this might be BB being overzealous in its blocking, but after doing more research it appears that the “Proxy-Connection” header is a non-standard, extended header not included in any HTTP specification.
It appears, according to HTTP: The Definitive Guide by David Gourley that this header is simply a hack to get around an issue with miscommunication between proxies.
After some more Googling, I found the simple fix:
In the Fiddler menu, select Rules › Customize Rules and then, in the OnBeforeRequest function, add this line:
Now Fiddler will no longer forward on this unnecessary header and Bad Behavior will be happy!