Hi,

Java has further enhanced security to make the user system less vulnerable to external exploits. Starting with Java 7 Update 51.

Java does not allow users to run applications that are not signed (unsigned), self-signed (not signed by trusted authority) or that are missing permission attributes.

Check out the below article to know more and to troubleshoot this issue;

https://www.java.com/en/download/help/java_blocked.xml