I'm using some free wordpress themes & would like to find a wordpress plugin that will check for exploits in my them. I tried the wordpress plugin "Exploit Scanner" and it just hangs is there another plugin to check for exploits & viruses etc.
Honestly the best way is to buy a cheap theme and a SSL certificate. Also keep current with all the updates because though the exploits do exist they get fixed pretty quickly.
There are so many reputable sources of quality free themes that this shouldn't be a problem. Just get your themes from trusted sources.
most of the time theme comes with encrypted footer or hidden links. You can check both of them watching it's source code. No extra plugin is required for the same. Try to avoid using such themes which is encrypted.