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Zoom Mac app flaw sparks serious security concerns—and it’s up to you to fix it

Credit: Zoom

If you’ve ever downloaded the Zoom app to participate in a video conference, your Mac may be at risk—even if you’ve already deleted it. In a Medium post, security researcher Jonathan Leitschuh discovered a serious flaw that could allow a website to access your Mac’s camera without your knowledge or permission.

As Leitschuh explains, the vulnerability stems from Zoom’s quest for simplicity. As the service works, you can just send anyone a Zoom meeting link which will in turn automatically open the Zoom client installed on their machine. In case you’ve deleted the app, Zoom keeps a localhost web server running silently on your Mac, Leitschuh said, so the Zoom client will reinstall when a link is clicked without requiring any user interaction on your behalf besides visiting a webpage.

That raises a whole lot of red flags. But even beyond the practice of surreptitiously running a localhost web server on hundreds of thousands of Macs around the world, Leitschuh unearthed a vulnerability that “allows any website to forcibly join a user to a Zoom call, with their video camera activated, without the user’s permission … and would have allowed any webpage to DOS (Denial of Service) a Mac by repeatedly joining a user to an invalid call.”

Leitschuh says Zoom dragged its feet on disclosing the vulnerability after being contacted in March, having only implemented a “quick fix” in late June. However, after he published the Medium post Monday, the company responded with a workaround rather than a true fix: “In light of this concern, we decided to give our users even more control of their video settings. As part of our upcoming July 2019 release, Zoom will apply and save the user’s video preference from their first Zoom meeting to all future Zoom meetings. Users and system administrators can still configure their client video settings to turn OFF video when joining a meeting. This change will apply to all client platforms.”

zoom flaw IDG

You’ll need to check this box to shut down the ability for websites to access your camera.

Zoom explains that changes implemented by Apple in Safari 12 that “requires a user to confirm that they want to start the Zoom client prior to joining every meeting.” In order to save users an extra click, Zoom installed the localhost web server as “a legitimate solution to a poor user experience problem.”