Google's Account Recovery Vulnerability: A Closer Look

A recent vulnerability in Google’s account recovery process exposed a critical flaw that allowed attackers to brute-force phone numbers linked to user accounts. This issue was discovered by the security researcher known as BruteCat, who reported it through Google’s Vulnerability Reward Program (Bleeping Computer). The flaw was found in a deprecated version of the Google username recovery form, which lacked essential anti-abuse protections. Attackers could exploit this form to systematically guess and verify phone numbers associated with specific Google account display names. This vulnerability highlights the ongoing challenges in securing online platforms and the importance of robust security measures (Android Authority).

Exploitation Methodology

The vulnerability allowed attackers to brute-force the recovery phone numbers tied to Google accounts by exploiting a deprecated version of the Google username recovery form, accessible when JavaScript was disabled. This form lacked modern anti-abuse protections, such as rate limiting and robust token validation mechanisms, making it susceptible to brute-force attacks. The attacker could systematically guess and verify phone numbers associated with specific Google account display names. This vulnerability was initially reported by the security researcher known as BruteCat (Bleeping Computer).

Vulnerability Discovery and Reporting

The vulnerability was discovered and reported by BruteCat through Google’s Vulnerability Reward Program (VRP) on April 14, 2025. Initially, Google assessed the exploitability risk as low. However, upon further evaluation, the severity was upgraded to medium on May 22, 2025. Google applied interim mitigations and rewarded the researcher with $5,000 for the disclosure (Bleeping Computer).

Technical Details of the Exploit

The attack leveraged the Google Looker Studio web analytics tool to obtain the display name tied to a Google account. The attacker could then use this information in conjunction with the vulnerable recovery form to brute-force the phone number. The form provided a hint by displaying the last two digits of the phone number, which facilitated the attack. The attacker would input various combinations until the correct phone number was identified (Android Authority).

Mitigation Measures Implemented by Google

Google responded to the vulnerability by deprecating the vulnerable no-JS recovery endpoint on June 6, 2025. This action effectively closed the attack vector, preventing further exploitation of the vulnerability. Google emphasized its commitment to working with the security research community to identify and address such issues promptly. The company acknowledged the importance of submissions from researchers like BruteCat in maintaining user safety (WIRED).

Potential Impact and Risks

The exposure of phone numbers linked to Google accounts posed significant risks to users. Phone numbers are a critical piece of information for SIM swappers, who could use them to execute phishing attacks or SIM swap attacks. These attacks could lead to unauthorized access to online accounts, identity theft, or financial fraud. The vulnerability also highlighted the broader implications of inadequate security measures in account recovery processes (Cyber Insider).

Google’s Response and Security Enhancements

Interim Mitigations

Before fully deprecating the vulnerable endpoint, Google implemented interim mitigations to reduce the risk of exploitation. These measures included enhancing rate limiting and token validation mechanisms to prevent brute-force attempts. Google also increased monitoring of account recovery processes to detect and respond to suspicious activity more effectively (Bleeping Computer).

Collaboration with Security Researchers

Google’s collaboration with security researchers through its VRP played a crucial role in identifying and addressing the vulnerability. The company has a long-standing history of engaging with the security community to enhance its products’ security. This collaboration not only helps in discovering vulnerabilities but also fosters a culture of proactive security measures (WIRED).

User Awareness and Education

In addition to technical mitigations, Google has emphasized the importance of user awareness and education in preventing security breaches. The company regularly updates its users on potential security threats and best practices for safeguarding their accounts. This includes encouraging users to enable two-factor authentication and use strong, unique passwords for their accounts (Android Authority).

Future Security Enhancements

Google has committed to further enhancing the security of its account recovery processes. This includes implementing more robust anti-abuse protections and exploring new methods for verifying user identities securely. The company is also investing in advanced threat detection technologies to identify and mitigate potential vulnerabilities before they can be exploited (Bleeping Computer).

Broader Implications for Online Security

Importance of Secure Account Recovery Processes

The vulnerability underscores the critical importance of secure account recovery processes in protecting user data. As online services increasingly rely on phone numbers for account verification and recovery, ensuring the security of these processes is paramount. Companies must implement robust anti-abuse protections and continuously update their security measures to address emerging threats (Cyber Insider).

Role of Security Research in Enhancing Online Safety

The discovery and reporting of this vulnerability highlight the vital role that security researchers play in enhancing online safety. By identifying and disclosing vulnerabilities, researchers help companies address security weaknesses before they can be exploited by malicious actors. This collaborative approach is essential for maintaining the integrity and security of online services (WIRED).

User Responsibility in Protecting Personal Information

While companies have a responsibility to secure their platforms, users also play a crucial role in protecting their personal information. Users should be vigilant about the information they share online and take proactive steps to secure their accounts. This includes enabling security features like two-factor authentication and regularly reviewing account settings for potential vulnerabilities (Android Authority).

The Evolving Threat Landscape

The vulnerability also highlights the evolving threat landscape that online services face. As attackers become more sophisticated, companies must continuously adapt their security measures to address new and emerging threats. This requires ongoing investment in security research, technology, and user education to ensure the safety and security of online platforms (Bleeping Computer).

Emerging Technologies and Future Risks

Emerging technologies like AI and IoT could potentially impact similar vulnerabilities in the future. As these technologies become more integrated into online services, they could introduce new security challenges. Companies must be proactive in understanding and mitigating these risks to protect user data effectively.

Final Thoughts

The discovery and subsequent patching of this vulnerability underscore the critical role of security researchers in maintaining the safety of online platforms. Google’s swift response, including the deprecation of the vulnerable endpoint and collaboration with the security community, demonstrates a proactive approach to cybersecurity (WIRED). However, this incident also serves as a reminder of the evolving threat landscape and the need for continuous investment in security technologies and user education. As attackers become more sophisticated, both companies and users must remain vigilant and proactive in protecting personal information (Cyber Insider).

References

• Google patched bug leaking phone numbers tied to accounts, 2025, Bleeping Computer source url
• Google account brute-force vulnerability, 2025, Android Authority source url
• A researcher figured out how to reveal any phone number linked to a Google account, 2025, WIRED source url
• Google flaw allowed brute-forcing users’ phone numbers, 2025, Cyber Insider source url