Sometimes, old versions of an applet stored in your cache can cause security conflicts. In the Java Control Panel, stay on the tab.

The "Application blocked by Java Security" error is a protective mechanism introduced by Oracle Corporation in Java 7 Update 51 (released January 2014) and strengthened in subsequent updates. It prevents untrusted, self-signed, or unsigned Java applications from running in a web browser or as standalone Java Web Start applications. This report details the root causes, security rationale, and step-by-step remediation strategies for both end-users and enterprise administrators.

Running an old version of Java can trigger security blocks.