Old versions of Java have been blocked - update and unblock Java

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  • Revision id: 23049
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  • Creator: Cheng Wang
  • Comment: I know the markup needs work but I'd like to get this page up sooner rather than later.
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Firefox recently added older versions of Java to its blocklist. A recent widespread attack exploits a vulnerability in older Java versions and could result in an attacker taking over your computer without your knowledge to access files or steal critical information like banking credentials. This article describes the steps to take to get Java working again.

Update Java

Firefox only blocks vulnerable versions of Java so the best thing to do is to update to a fixed version. Unfortunately, simply installing a new version of Java doesn't necessarily remove older Java versions from your computer, leaving you vulnerable.

  1. Go to the Java download page and download the latest Java installer.
  2. Click the Firefox menu Fx89menuButton and select Exit.Click the Firefox menu at the top of the screen and select Quit Firefox.Click the Firefox menu Fx89menuButton and select Quit.
  3. In Windows, go to the Control Panel (usually from your Start menu) and select Add/Remove Programs. (This may be called Programs or Programs and Features)
  4. Look for any Java or Java Runtime programs, select them and click Remove or Uninstall for each one. Complete the uninstall process before proceeding.
  5. Run the installer you downloaded in step 1.
  6. Start Firefox
  1. Go to the Java download page and download the latest Java installer.
  2. Click the Firefox menu Fx89menuButton and select Exit.Click the Firefox menu at the top of the screen and select Quit Firefox.Click the Firefox menu Fx89menuButton and select Quit.
  3. Run the installer you downloaded in step 1.
  4. Start Firefox
  1. Click the Firefox menu Fx89menuButton and select Exit.Click the Firefox menu at the top of the screen and select Quit Firefox.Click the Firefox menu Fx89menuButton and select Quit.
  2. From the Apple menu, select Software Update....
  3. Select the Java update and click Install. Wait for the update to complete.
  4. Start Firefox

Java should now work as expected. If you had previously selected Disable in the blocking dialog, you may need to enable Java again:

  1. From the Firefox menu (or the Tools menu) select Add-ons

  1. From the Tools menu select Add-ons
  1. Select the Plugins tab
  2. Find the Java Platform or Java Runtime item and click Enable.

Working around the blocklist

If you are unable to update Java, you can re-enable Java by working around the blocklist.

Warning: This leaves you vulnerable to attacks. Simply browsing to a compromised website could result in your computer being exploited.

Enabling Java

  1. From the Firefox menu (or the Tools menu) select Add-ons

  1. From the Tools menu select Add-ons
  1. Select the Plugins tab
  2. Find the Java Platform or Java Runtime item and click Enable.

If there isn't an Enable option, your blocklist may not be incorrectly hard-blocking. You can fix this by doing the following:

  1. From the Help menu, select Troubleshooting Info
  1. Click Open Containing Folder. Firefox will open your profile folder. Leave this folder open.
  2. Click Show in Finder. Firefox will open your profile folder. Leave this folder open.
  1. Click Open Containing Folder. Firefox will open your profile folder. Leave this folder open.
  2. Click the Firefox menu Fx89menuButton and select Exit.Click the Firefox menu at the top of the screen and select Quit Firefox.Click the Firefox menu Fx89menuButton and select Quit.
  3. In the profile folder that you opened earlier, find blocklist.xml (this may be listed as a "XML document" called blocklist) and pluginreg.dat (this may be listed as a "DAT document" called pluginreg). Delete both these files.
  4. Start Firefox
  5. You will be presented with the Add-ons may be causing problems window with Java listed. Uncheck the Disable box and click Restart Later.

You should now be able to use the older, insecure version of Java.