Private Data Leaked on Zoom after a Bug Discovered

Posted on by Dawna M. Roberts in News March 31, 2021

 Since the pandemic began, Zoom has become the go-to solution for meetings, classes, and business conferences. However, Zoom is not without its share of issues. Recently a new bug was discovered that may have leaked private data while users shared their screen.

What is the Problem?

The bug labeled (CVE-2021-28133) occurs when a participant on a call shares their screen. What it does is briefly displays other parts of the presenter’s screen, possibly leaking emails, passwords, or other private data to the other members on the call. Even though the bug displays the screen contents briefly, it is still enough time for someone to take a screenshot and capture it to use for identity theft or fraud.

German threat researchers Michael Strametz and Matthias Deeg discovered the bug and disclosed the details in a report on Thursday. Deeg told ThreatPost that “The impact in real-life situations would be sharing confidential data in an unintended way to unauthorized people.”

ThreatPost explained that “The issue occurs in a “reliably reproducible manner” when a user shares one split application window (such as presentation slides in a web browser) while opening other applications (such as a mail client) in the background, in what is supposed to be in non-shared mode. Researchers found the contents of the explicitly non-shared application window can be perceived for a “brief moment” by meeting participants.

While this would only occur briefly, researchers warn that other meeting participants who are recording the Zoom meeting (either through Zoom’s built-in recording capabilities or via screen recording software like SimpleScreenRecorder) are able to then go back to the recording and fully view any potentially sensitive data leaked through that transmission.”

Because someone with the intent to use the information would have to be on the call, the bug is rated with only medium severity. The threat assessors created a proof-of-concept video showing how it could work and tested it thoroughly.

How Did Zoom Respond?

The team that discovered it alerted Zoom on December 2; however, they have not yet seen an update from Zoom to fix the issue even after their report last Thursday.

In their discussion with ThreatPost, they said,

 “Unfortunately, our questions concerning status updates on January 21 and February 1, 2021, remained unanswered. I hope that Zoom will soon fix this issue, and my only advice for all Zoom users… is to be careful when using the screen sharing functionality and [to follow a] strict ‘clean virtual desktop’ policy during Zoom meetings.”

When ThreatPost reached out to Zoom for comment, they said,

 “Zoom takes all reports of security vulnerabilities seriously. We are aware of this issue and are working to resolve it.”

How Can Zoom Users Stay Safe?

As the pandemic continues to roll on, you cannot avoid using Zoom. Therefore take a few security precautions when doing so.

  • Use a stock background on your Zoom account rather than display the contents of the room you are in.
  • Refrain from opening any passwords, emails, or other sensitive information on your computer while on a Zoom call.
  • Always update your apps, including Zoom, to the latest version. 
  • Be sure you don’t have personal documents, your driver’s license, or other things with personally identifiable information (PII) on them lying around during a Zoom call. Someone could easily take a screenshot, blow it up and get your information that way for identity theft.
  • Take the time to go through Zoom and set your privacy and security options to the maximum available. 
  • Passwords protect all your Zoom calls so no one can inadvertently join the meeting without you knowing it.

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