User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:35.0) Gecko/20100101 Firefox/35.0 Build ID: 20150113033800 Steps to reproduce: 1. Go to https://stackoverflow.com 2. Open the Firefox Developer Tools 3. Go to the "Network" tab 4. Do a full reload (Ctrl-Shift-r) At this point, I get the error message "Stack Overflow requires external JavaScript from another domain, which is blocked or failed to load." This turned out to be jquery.min.js from ajax.googleapis.com, so I tried debugging: 5. Right-click jquery.min.js and select "Edit and Resend" 6. Remove the line starting with "DNT:" 7. Click "Send" Actual results: After clicking on the new request it showed a "DNT" header with the same value as the original request. I also tried changing the privacy setting to "Do not tell [...]", and it *still* inserted the original "DNT" header. Expected results: The "DNT" header should not have been included in the request.

This was tested on a completely new profile.

Fixed in bug 1270096.