Unfortunately it looks like your site has been compromised by the vulnerability in JCE versions prior to 2.9.99.5
Please see - https://www.joomlacontenteditor.net/news/jce-security-update-and-a-free-patch-for-older-sites
Ryan Demmer
Lead Developer / CEO / CTO
Just because you're not paranoid doesn't mean everybody isn't out to get you.