You are right, I have not installed the extension.

Hopefully the file name could also be corrected without the extension.

• Browser: Chrome 52.0.2743 Windows 8.1
• User Agent: Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/52.0.2743.116 Safari/537.36

I'm using the website. Practically every clip are the same, one example would be https://www.youtube.com/watch?v=U5Y0uQLgriA