For example, say, I open this youtube page: https://www.youtube.com/watch?v=e-ORhEE9VVg Firefox opens it and whithin 5 seconds, with no action on my part - no clicking, typing, nothing - transfers me over to: https://r7---sn-8p85jvh-nv4e.googlevideo.com/videoplayback?mm=31&source=youtube&ratebypass=yes&dur=272.462&mt=1423341461&mv=m&ms=au&fexp=907263%2C924628%2C927622%2C930676%2C943917%2C945098%2C947225%2C948124%2C948909%2C952302%2C952605%2C952612%2C952901%2C955301%2C957201%2C959701&ip=79.100.24.238&upn=3_qYUmHqoVM&id=o-ALB3CMI8PMR7Ylk-0D_a76ghgOzcADyQvQ21B3HCYCCW&sparams=dur%2Cid%2Cinitcwndbps%2Cip%2Cipbits%2Citag%2Cmime%2Cmm%2Cms%2Cmv%2Cpl%2Cratebypass%2Crequiressl%2Csource%2Cupn%2Cexpire&initcwndbps=1272500&expire=1423363109&sver=3&pl=20&requiressl=yes&mime=video%2Fmp4&key=yt5&itag=22&ipbits=0&fallback_host=tc.v7.cache5.googlevideo.com&quality=hd720&signature=D5CA5BD786DB0F73296165DE1C2EDE972A6EAAF353.893EB11517D389BCA3436ADEE89CF0D6C2D60E2420&title=Taylor%20Swift%20-%20Blank%20Space%20%28HD%29 Which sometimes stays in the address bar over a completely blank window, (like in the case stated above) and sometimes opens a download window, with the video in mp4. It suggests I open the file with VLC. Is this a virus or something - or is it something an add-on would be responsible for? I have the following add-ons (in the way that they are listed on my toolbar): Down them all Download Helper Flash Video Downloader (which recently got automaitically updated) Download flash & video (forgot this add-on's name, that's what it says on the tool tip on mouse-over) FlashGot and GreasMonkey (but with only 2 scripts, and none of them related to videos, just IMDb fixer and Image enlarger) I have the VLC Media Player Plug-in, could this be the reason this is happening? I know what you're gonna say - try disabling them to see which one it is. It's complicated :) but I can't, I've got too many windows open, like 700, and shutting Firefox down or restaring it the normal way is near next to impossible sometimes :) Another way is for me to save my session file and open a new session, and then disable add-ons one by one to see which one's to blame. It's even possible some of them are maybe incompatible with this version of Firefox. So f someone can tell me if they're having the same problems, and maybe suggest a solution, I'd be happy to hear all about it. Thanks in advance :)