JClass supports Microsoft Internet Explorer but we don't have such document indicating which versions of IE can or cannot be supported, so in our tests for the latest version of JClass, we've used IE 9, IE 10 and IE 11 to validate the function.
For such question, it's related to the plug-ins(such as Adobe, JRE), JClass can support the IE browsers on which compatible plugin-ins installed. You could have a test for IE 11 on test environment before the upgrade.