A flaw in Zoom’s Vanity URL feature could have been exploited in phishing attacks

Pierluigi Paganini July 20, 2020

A vulnerability affecting the Zoom feature dubbed Vanity URL could have been exploited by hackers for phishing attacks.

A vulnerability affecting the Zoom feature dubbed Vanity URLs could have been exploited by hackers for phishing attacks.

The popularity of the Zoom video conferencing service exploded during the COVID-19 outbreak when it was chosen by organizations, schools, and private users as a collaboration platform tool.

Recently researchers from Check Point discovered a vulnerability in the Zoom Vanity URL, a feature that allows users to create a ‘Vanity URL,’ which is a custom URL for your company (i.e. yourcompany.zoom.us).

Organizations could use the Vanity URL mechanism to create a customized version of Zoom’s invitations links.

“Prior to Zoom’s fix, an attacker could have attempted to impersonate an organization’s Vanity URL link and send invitations which appeared to be legitimate to trick a victim.” reads the analysis published Check Point. “In addition, the attacker could have directed the victim to a sub-domain dedicated website, where the victim entered the relevant meeting ID and would not be made aware that the invitation did not come from the legitimate organization.”

The issue could be exploited by attackers to trick victims into believing that the invitation they have received was sent from the company’s Vanity URL.

In the attack reported by the experts, the URL would actually point to a subdomain registered by the attacker with a name that looks like the one of the target.

With this attack scheme, the attacker aims at tricking the victims into handing over credentials or other sensitive information.

“if the original invitation link was https://zoom[.]us/j/7470812100, the attacker could change it to https://<organization’s name>[.]zoom[.]us/j/7470812100. A victim receiving such an invitation would have had no way of knowing the invitation did not actually come from the actual organization.” continues the analysis.

“In addition, the attacker could also change the link from /j/ to /s/: https://<organization’s name>[.]zoom[.]us/s/7470812100. Given there are cases of organization’s logos appearing when entering such a URL, this could have added an additional layer of deception. Also, clicking on the “Sign in to Start” button, would often lead the victim to the organization’s legitimate portal. This issue impersonated relevant organizations using the Vanity URL capability.”

Check Point researchers revealed that an attacker could also target the dedicated Zoom web interfaces used by some organizations use for video conferencing. They could exploit the flaw by redirecting the user to a malicious Vanity URL.

“A user can enter any meeting ID in this screen, whether it was originally scheduled by the organization’s employee or not, and join the relevant Zoom session.” said the experts. “An attacker could have invited the victim to join the session through the dedicated website, and the victim would have had no way of knowing the invitation did not actually come from the legitimate organization.”

CheckPoint has cooperated with Zoom to address the vulnerabiltiy.

“All the details of how an attacker could impersonate an organization’s Zoom subdomain links or actual sub-domain website discussed here were responsibly disclosed to Zoom Video Communications, Inc. as part of our ongoing partnership and cooperation.  This security issue has been fixed by Zoom, so the exploits described are no longer possible.” Check Point concludes.

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Pierluigi Paganini

(SecurityAffairs – hacking, Zoom Vanity URL)

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