In the past, to protect you from plugins that have stability or security issues, Firefox could only turn off the problematic plugin. Now Firefox can prevent the plugin from running automatically (which prevents many issues) and then let you choose to run or update the plugin. Here's how it works.
Updating a plugin is always the safest thing to do but, sometimes, it may not be possible. For example, you may not be allowed to update a computer at work or school. In a situation like this, you can make a smart choice depending on your current task:
If you are unable to update a plugin and you are using a trusted site, you can set that plugin to automatically run whenever using that site:
Now, whenever you visit this site, the plugin will automatically run and you won't get the "Click to activate" message.