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After I've updated Java to version 7 update 17 it no longer activates 'click-to-play' when I am browsing to a site that uses Java. I really like to put it back to 'click-to-play' list in light of Java security problems coming out weekly.

I know that you can turn on 'click-to-play' globally (for all plugins) through 'plugins.click_to_play' in 'about:config'.

However, I think it's a very blunt instrument.

I tried to find any documentation about 'click-to-play', but looks like it's really well hidden by Mozilla developers.

What I really would like to understand is where is the 'magic' block list of plugins maintained: locally, or on Mozilla web site? If it is local, where is it?


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I'm not sure the feature is worth a whole tag just yet. firefox is enough for now. You may also want to specify your Firefox version in the question body, though. – Iszi Mar 5 '13 at 17:00
@Iszi 19.0 on Windows 7. – Alexander Pogrebnyak Mar 5 '13 at 18:30
file:///C:/Program%20Files%20%28x86%29/Mozilla%20Firefox/blocklist.xml – Wk_of_Angmar Mar 7 '13 at 20:14
up vote 1 down vote accepted

The "click to play"-functionality is still not completed. A per-addon / per-plugin blocking management via about:config or even a GUI seems not to be available.

As @Wk_of_Angmar already pointed out, the file blocklist.xml defines what is deemed unsafe by the browser. It is stored locally, but refreshed periodically(default: every 86400 seconds = daily) from the Mozilla servers; the behavior can be controlled by Extensions.blocklist.interval. If you now want your Java applets to be set to click to play, you would have to do three things:

  1. Add an entry for your specific Java version in the blocklist file(Syntax here, you should look into pluginItem specifically)

  2. Prevent Firefox from updating the file and therefore overriding your entry. A possibility I could think of would be setting ´Extensions.blocklist.interval´ to a very high number or making the file read-only.

  3. Remember to update the blocklist from the URL defined here manually.

It is not pretty, but should work while CTP is still under development.

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