My website was hacked. Any suggestions?

My website was hacked recently, and I wanted to see if you had any suggestions.

I think they exploited the site using a security hole that was in one of the plugins that needed to be updated. When I found the damage, I immediately updated the plugins and WordPress, as well as, adding some more security features. The weird thing is they were able to change the Title, Description and Keyword meta tags in my Header, as well as, installing hidden text in the Body of the pages. This shows up in Google’s cache for Una Ola. The compromise is clearly visible in the code, however, when you look at Una Ola (not Google’s cached page), none of this is visible in the code. I’m baffled as to how they are able to get the Googlebot to view it as compromised in the SERP results without it showing in the actual page code.

Let me know if you have any ideas or suggestions on how to resolve this.