Hundreds of millions of users of Grammarly, Vidio, and Bukalapak are at risk due to critical API misconfigurations in the implementation of the OAuth standard. These flaws could have allowed attackers to take over user accounts, leading to credential theft, financial fraud, and other cybercriminal activities.
Researchers from Salt Labs discovered these issues, which they refer to as a “Pass-The-Token” flaw, enabling attackers to use tokens from third-party sites to access other services. While the flaws in the mentioned services have been resolved, the researchers warn that many other websites may also be vulnerable to such attacks.
The issue manifests uniquely on each of the three sites. For instance, Vidio, a platform with 100 million monthly active users, failed to verify tokens when logging in through Facebook, enabling attackers to manipulate API calls and insert unauthorized access tokens.
Bukalapak, with over 150 million monthly users, exhibited a similar vulnerability when users registered using social logins. Grammarly, used by over 30 million daily users for grammar and writing tips, had a different manifestation of the OAuth flaw, which allowed attackers to manipulate API exchanges to access user credentials and achieve account takeover.
The OAuth standard itself is well-designed, but many services that implement it suffer from misconfigurations, creating security vulnerabilities. Proper knowledge and awareness are crucial in implementing OAuth securely, as attackers can exploit vulnerabilities easily, potentially affecting numerous users. Developing services using OAuth should ensure a solid understanding of the protocol and its potential pitfalls. Additionally, developers can employ third-party tools to monitor anomalies and deviations from normal behavior, helping identify unknown attacks and protect users.
