User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/42.0.2311.152 Safari/537.36 Steps to reproduce: Hi team , im just found this bug in mozila firefox browser i test it on the latest version developer edition 64 bit and i think is on all the version of your browser , the bug allow me to crash the browser and block all the website opening on it . with just a simple javascript code which i can add into the javascript console on the browser : the code is var num = 1; while (num <= 20) { document.write(num+" "); } this is a video poc of this bug : https://www.youtube.com/watch?v=E2l4gHW2Edk thanks to respond ==> lahlousecom@gmail.com Actual results: High level Crashing in the browser ! Breack all the Website connected on it !!