There are two methods to upgrade Java Plugin in Firefox Portable. First is the recommended one — download JPortable and put it in the same PortableApps dir where your Firefox resides, that is you should get following structure:
- PortableApps/CommonFiles/Java — here you have JPortable
- PortableApps/FirefoxPortable — here you have Firefox
There is another way to accomplish the same task. It is useful for instance if you have dozen of portable Firefoxes installed. Suppose you’re a web developer and you want to test your website or firefox extension against multiple versions of Firefox. In this case you can go here download and install jxpiinstall.exe. Then you automatically get the latest Java plugin in all Firefoxes you have installed.