Account Takeover via Authentication Bypass in TikTok Account Recovery

Summary

An improper authentication mechanism in TikTok's account recovery process could have been used for account takeovers on Android devices. There was no evidence of exploitation and this vulnerability has now been completely fixed. We thank @xtt0k for reporting this to our team and confirming its remediation.

I identified a critical vulnerability in one of TikTok's endpoints that permitted unauthorized changes to user accounts due to improper parameter handling. This flaw could have allowed a TikTok account to be taken over by knowing the account username. I appreciate TikTok's swift action in resolving this issue and their generous bounty.