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About Firefox Monitor Firefox Monitor warns if your online accounts were involved in a data breach. Find out if you’ve been in a data breach, get alerts about new breaches, and take steps to protect your online accounts. Firefox Monitor is provided by Mozilla. About Firefox Monitor. Firefox Monitor warns if your online accounts were involved in a data breach. Find out if you’ve been in a data breach, get alerts about new breaches, and take steps to protect your online accounts. Firefox Monitor is provided by Mozilla.

See if you’ve been involved in an online data breach.

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Download Greasemonkey for Firefox. Customize the way a web page displays or behaves, by using small bits of JavaScript. Find out if you’ve been part of a data breach with Firefox Monitor. Sign up for alerts about future breaches and get tips to keep your accounts safe. Most people have about 100 online accounts.

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Learn everything you need to know (but don’t yet) about staying smart and safe online, from some of the world’s foremost experts.

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