[technology taskforce] Test your browser config if it launches Zoom automatically with camera and mic enabled

Dev Anand Teelucksingh devtee at gmail.com
Thu Jul 11 16:29:23 UTC 2019

The security researcher Jonathan Leitschuh who publicly disclosed the Zoom
security vulnerability has noted that depending on your browser setting on
whether to always open Zoom links with the associated app is on, a
malicious webpage (that could be hidden in a iframe) can automatically
launch Zoom with your camera enabled without asking. This is true for
Windows as well as for Mac for Firefox and Chrome browsers.

As he noted in his tweet at

Here is a Proof of Concept Link to see whether Zoom will autolaunch with
your camera and mic enabled :

If your browser settings are set to always these type of Zoom links with
the associated app, you *will* be automatically launched into a Zoom
conference with your camera enabled.

How to prevent Zoom from auto-opening Zoom links on a webpage :

In Mozilla Firefox,
- 1) Click the menu button [image: Fx57Menu] and choose Options.
- 2) In the General panel, go to the *Applications* section.
3) Search for the Content Type *zoommtg* and select it.
4) Click on the Action column in the *zoommtg* row to change the
action to "*always
[image: firefox-turning-off-automatic-open-zoom.png]

In Google Chrome:

This is harder for Google Chrome which saves such settings in a preferences
file which isn't accessible from the browser.

>From https://support.google.com/chrome/answer/114662

"Chrome allows external applications and web services to open certain
links. For example, certain links can open a site like Gmail or a program
like iTunes. If you set a default action for a type of link but want to
delete it, clear your browsing data
<https://support.google.com/chrome/answer/2392709> (
https://support.google.com/chrome/answer/2392709) and select "Cookies and
other site data."

Here's the more "hacky" way:
1) Navigate to chrome://version/ and find the path listed under "Profile
2) Quit Chrome, open that directory, and then open the "Preferences" file.
This will appear be a long line of text in a text editor.
3) Look for the string "zoommtg":false or "zoomrc":false. If it either
exist, remove them. If there is a comma immediately after either string,
remove it as well.
4) Save the file.

Visit Jonathan Leitschuh's Proof of Concept page at *
<https://jlleitschuh.org/zoom_vulnerability_poc/zoompwn_iframe.html>* to
see if your browser asks to open Zoom.

This is what you will see in Mozilla Firefox :
[image: firefox-ask-to-launch-zoom.png]

and this is what you will see in Google Chrome:

[image: chrome-ask-to-launch-zoom.png]
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