That particular compromise looks to be started from the demo_oleg/wp6 Wordpress install, which is running version 3.8 and is 9 months out of date (3.8 launched last December). With compromises of this nature, you would be responsible for cleanup as account security is the user's responsibility, and if we attempt cleanup there's a very good chance we would actually damage the site further. With us only having full-server backups, we wouldn't be able to restore an individual website from them either, so if we were to make things worse by accident we wouldn't be able to fix it.
If you have backups, I would recommend removing everything on the account and starting from a backup that wasn't infected, then immediately update all software to their latest versions. If no backups are available, then I would instead remove all files and start from fresh, vendor supplied files that are up-to-date only, as any outdated software with known exploits is a target for hackers as soon as they discover the location of it.