TikTok, the 3rd most downloaded app in 2019, is under intense scrutiny over users’ privacy, censoring politically controversial content and on national-security grounds—but it’s not over yet, as the security of billions of TikTok users would be now under question.

The famous Chinese viral video-sharing app contained potentially dangerous vulnerabilities that could have allowed remote attackers to hijack any user account just by knowing the mobile number of targeted victims.

In a report privately shared with The Hacker News, cybersecurity researchers at Check Point revealed that chaining multiple vulnerabilities allowed them to remotely execute malicious code and perform unwanted actions on behalf of the victims without their consent.

The reported vulnerabilities include low severity issues like SMS link spoofing, open redirection, and cross-site scripting (XSS) that when combined could allow a remote attacker to perform high impact attacks, including:
 

• delete any videos from victims’ TikTok profile,
• upload unauthorized videos to victims’ TikTok profile,
• make private “hidden” videos public,
• reveal personal information saved on the account, such as private addresses and emails.

The attack leverages an insecure SMS system that TikTok offers on its website to let users send a message to their phone number with a link to download the video-sharing application.
 

According to the researchers, an attacker can send an SMS message to any phone number on behalf of TikTok with a modified download URL to a malicious page designed to execute code on a targeted device with already installed TikTok app.
 

When combined with open redirection and cross-site scripting issues, the attack could allow hackers to execute JavaScript code on behalf of victims as soon as they click the link sent by TikTok server over SMS, as shown in the video demonstration Check Point shared with The Hacker News.

The technique is commonly known as cross-site request forgery attack, wherein attackers trick authenticated users into executing an unwanted action.

“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,” the researchers said in a blog post published today.

“Redirecting the user to a malicious website will execute JavaScript code and make requests to Tiktok with the victims’ cookies.”

Check Point responsibly reported these vulnerabilities to ByteDance, the developer of TikTok, in late November 2019, who then released a patched version of its mobile app within a month to protect its users from hackers.

If you are not running the latest version of TikTok available on official app stores for Android and iOS, you’re advised to update it as soon as possible.