Pierluigi Paganini January 08, 2020

A flaw in the popular TikTok app could allow attackers to hijack any user account just by knowing the mobile number of the victim.

Security experts from CheckPoint have discovered a critical vulnerability in the popular TikTok app that could be exploited by a remote attacker to hijack any user account just by knowing the mobile number of the victim

TikTok is a social media app that allows its users to create and share short form videos.

The app developed by the Chinese firm ByteDance has over 1.3 billion installs worldwide, it has come under close scrutiny in the US and other countries for its alleged link with the Government of Beijing.

All free accounts are by default public, only subscribers could restrict the access to the accounts’ content.

Check Point researchers discovered multiple low severity vulnerabilities that could be chained by remote attackers to execute malicious code on the target system and perform unwanted actions.

The vulnerabilities include SMS link spoofing, open redirection, and cross-site scripting (XSS).

“In the recent months, Check Point Research teams discovered multiple vulnerabilities within the TikTok application.” reads the analysis published by CheckPoint. “The vulnerabilities described in this research allow attackers to do the following:

• Get a hold of TikTok accounts and manipulate their content
• Delete videos
• Upload unauthorized videos
• Make private “hidden” videos public
• Reveal personal information saved on the account such as private email addresses”

The attack devised by CheckPoint leverages a feature implemented by the popular app that allows sending an SMS message to any phone number on behalf of TikTok.

TikTok’s website (www.tiktok.com) implements functionality that lets users send an SMS message to their phone number to download the app.

The experts discovered that it is possible to abuse the feature to send an SMS message to any phone number on behalf of TikTok that contains a malicious URL instead of the legitimate download URL. The URL points to a specially-crafted page designed to execute code on a targeted device with already installed the TikTok app.

Chaining open redirection and cross-site scripting issues it is possible to carry out a cross-site request forgery attack, the attackers could execute JavaScript code on behalf of victims as soon as they click the link sent by TikTok server over SMS.

“At this point, we had two different flows that we could execute JavaScript code on behalf of any victim that clicked the link we sent (as explained in SMS Link Spoofing) – XSS and open redirection (redirecting the user to a malicious website that will execute JavaScript code and make requests to Tiktok with the victims’ cookies).” continues the analysis.

“With the lack of anti-Cross-Site request forgery mechanism, we realized that we could execute JavaScript code and perform actions on behalf of the victim, without his/her consent,” “Redirecting the user to a malicious website will execute JavaScript code and make requests to Tiktok with the victims’ cookies.”

Check Point responsibly reported the flaws to the company ByteDance in November 2019, and the firm released a new version to address them a month later.

CheckPoint researchers also published a video PoC of the attack:

https://research.checkpoint.com/wp-content/uploads/2020/01/tiktok_video.mp4?_=1

Pierluigi Paganini

(SecurityAffairs – TikTok, hacking)

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