A security glitch in Zoom’s screen-sharing feature could potentially put users’ data at risk. The flaw briefly lets people see parts of a presenter’s screen that shouldn't have been visible at all.
That means the presenter could inadvertently be broadcasting sensitive information, such as usernames and passwords, without even realizing it. Plus there’s always the potential for embarrassing stuff to show up at the same time.
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Zoom gives presenters the option to share a view of their entire screen, certain applications, or a very select area of the screen. This new flaw, discovered by SySS security consultants Michael Strametz and Matthias Deeg (opens in new tab), means that “under certain conditions” the single-application view doesn't work correctly.
Rather than broadcasting one app, and only one app, viewers would briefly be able to see other windows on a presenter’s screen.
The researchers found that other applications were only open for “a brief moment”, but that may well be enough for a vigilant viewer to get a glimpse of sensitive information.
That’s especially concerning if any participants are recording the meeting. Even if people can’t register any information during the brief moment the other screens are visible, viewers could go back through their recordings and snoop around.
Of course there are difficulties in exploiting this bug, since it would rely on an attacker actually being present on the call in the first place. The severity also depends on how the kind of data that’s shared. Items like the screens of password managers would be a major concern, as would the contents of sensitive emails.
Then again, if other Zoom meeting participants saw you looking at a Reddit page of cute animals, it wouldn't be as serious a problem. It may be a little embarrassing for that to be on display to everyone, but it’s not going to negatively impact your life.
The flaw was reported to Zoom on December 2, but the researchers say that they are “not aware of a fix”. The current version of Zoom for Windows, version 5.5.4 (13142.0301), is still vulnerable, and researchers say the problem can occur in a “reliably reproducible manner”.
Zoom told Threatpost (opens in new tab) that it is aware of the issue and is working to resolve the problem. In the meantime, you should be more careful about the things you do while presenting on Zoom. Don’t open any applications you want to keep private.
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