User Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:35.0) Gecko/20100101 Firefox/35.0 Build ID: 20150125221831 Steps to reproduce: Visit "http://localhost/?a[0]=a" Open console and type "location.search" Actual results: "?a%5B0%5D=a" Expected results: "?a[0]=a"

I see now that this problem also affects the URL bar. If you copy the URL from the bar, the clipboard will now have an encoded version. Also the "Copy as CURL" is affected and I guess anywhere the URL of a site is retrieved. Maybe also the request hitting the server is mangled. Chrome handles this correct in mentioned situations.