Recently there have been some pretty big security issues found with several browser plug-ins. Like this huge one for the WebEx in Chrome issue
It is best that, if you must use them, you manually update them. Please always keep your stuff updated.
To force update Chrome extensions:
Open Chrome, then got to Settings – clicking on the three vertical dots in the top right of Chrome.
Then click on Extensions:
Next Click on ‘Developer mode’ then click on “Update extensions now”
For Firefox you need to update addons and plug-ins: