For some reason i had the same problem and my co-workers account seem to be hacked too, weird that it happen at the same time as you. My site was redirecting to this scam domain (sleth info), was your site redirecting to the same?
I don’t see other users mentioning a specific vulnerability in this plugin’s support forum yet. Would you let the developers know, so they can have a look at what you perceive as a problem in their plugin? If in fact there’s a problem with their code, a fast resolution would help many of their users [WP Fastest Cache] Support | WordPress.org