This is a complete new feature on RuneLocus.
It is a simple but effective ByteCode scanner. The purpose of this little tool was to scan class(es) in JARs (as well as any ZIPs and RARs) for any code that can be malicious at some moment. As well as scanning compressed files which contain many classes, you can scan single classes.
This application specifically looks for any outgoing / incoming connections, any type of access to files on your computer (deletion / creation), shell commands and the loading of external libraries which can be malicious.

You can visit the ByteCode Scanner at this page, and under the 'Tool' category on the left navigation bar.

Notice: A warning does not instantly mean the file is malicious and should not be trusted!
A warning means there is a possible chance it's malicious, but the chance is usually small.