When Facebook users learned last March that the social media giant had given their sensitive information to political-data firm Cambridge Analytica, Mozilla (parent company of the security-focused browser Firefox) reacted fast: Within eight hours, the product team had built a browser extension called the Facebook Container. The plug-in, now the most popular browser extension Mozilla has ever built (1.5 million downloads and 500,000 monthly active users), prevents Facebook from trailing its users around the internet. Firefox Monitor, a service Mozilla launched in September, uses your email address to determine whether your personal info has been compromised in a breach. By summer 2019, the Firefox browser will also block, by default, all cross-site third-party trackers, strengthening privacy without your having to do a thing (unlike Firefox’s biggest competitor, Google Chrome). “We want to make it simple for people to create walls around data that’s important to them,” says Denelle Dixon, Mozilla’s COO.