Starting with Java 7 Update 51, applets that do not conform with the latest security practices can still be authorized to run by including the sites that host them to the Exception Site List.
Starting with Java 8 Update 20, the Medium security level has been removed from the Java Control Panel. Only High and Very High levels are available.
The exception site list provides users with the option of allowing the same applets that would have been allowed by selecting the Medium option but on a site-by-site basis therefore minimizing the risk of using more permissive settings.
Applications signed with the MD5withRSA or MD5withDSA algorithms are
treated as unsigned starting with the Java 8 Update 131 release.
Error Messages/Dialogs:
MD5withRSA Algorithm
Unable to launch application.
Unsigned application requesting unrestricted access to system
The following resource is signed with a weak signature algorithm
MD5withRSA and is treated as unsigned:
http://example.net/ExampleApplication.jar
MD5withDSA Algorithm
Unable to launch application.
Unsigned application requesting unrestricted access to system
The following resource is signed with a weak signature algorithm
MD5withDSA and is treated as unsigned:
http://example.net/ExampleApplication.jar
Application users
If you encounter either of the messages above, it is recommended that
you contact the website where you are seeing this message or the
application vendor and provide them with the message. The website or
vendor needs to improve the security of the application, as the
application is no longer secure using MD5withRSA or MD5withDSA.
Application developers
If you own, develop or maintain a Java application that is displaying these
messages, it is recommend that you re-sign the JAR with a stronger
algorithm. For information on how to identify the algorithm used to sign a
JAR, see the Changes section of the Java 8 Update 131 Release Notes. Additional information on using the Jarsigner tool can
be found on the Jarsigner Tool page. It is possible, but
not recommended, to update a client machine to revert this security
enhancement. Information on reverting can be found on the
Cryptographic Algorithms page.