Search function hacked

Hello!
I do not know when happened this, but I just discovered that if I type anything in my search are from my blog, I get a white page with this message:
”By OvErDz [+] FUCK ISRAEL”
I also could not log in into the wp-admin area because the password was changed. I managed to changed it by editing the wp-user table via phpmyadmin.
I updated everything and even ran a scan using Wordfence but did not find anything.
The rest of the blog is totally functional.

What do I have to do to fix the search option and get rid of that message?
Thank you.