CVE-2025-61116 identifies a security vulnerability in the AdForest Classified Android app version 4.0.12, developed by Muhammad Jawad Arshad. The core issue lies in the app's authentication mechanism, which improperly uses a Base64-encoded email address as the authorization credential. Base64 encoding is not encryption and can be easily decoded or manipulated by attackers. This weak authorization scheme allows attackers to craft or alter the Base64-encoded email string to impersonate other users and gain unauthorized access to their accounts. Such unauthorized access can lead to account takeover, exposure of personal and sensitive user data, and potential misuse of the platform for fraudulent activities or spreading misinformation. The vulnerability stems from improper access control and inadequate validation of authorization tokens. No CVSS score has been assigned yet, and there are no known exploits in the wild, but the flaw presents a significant risk due to the ease of manipulation and the sensitive nature of user accounts. The vulnerability does not require user interaction but does require the attacker to know or guess valid email addresses associated with the app. The lack of patch links indicates that a fix may not yet be available, emphasizing the need for immediate attention from developers and users. This vulnerability highlights the importance of using secure authentication tokens and robust access control mechanisms in mobile applications, especially those handling user accounts and personal data.

For European organizations, this vulnerability poses a risk to user privacy and data confidentiality, especially for businesses or platforms relying on the AdForest app or similar classified ad services. Compromised accounts could lead to unauthorized transactions, fraudulent postings, or exposure of personal information, potentially violating GDPR and other data protection regulations. The integrity of the platform could be undermined by attackers manipulating account data or posting malicious content. Availability impact is limited but could occur if attackers disrupt user access or flood the platform with fraudulent activity. The reputational damage to organizations supporting or affiliated with the app could be significant, leading to loss of user trust. Given the app’s presence on Android devices, the threat surface includes a wide range of users, increasing the potential scope of impact. European companies involved in classified advertising, online marketplaces, or mobile app development should be particularly vigilant.

Developers should immediately revise the authentication mechanism to replace the Base64-encoded email authorization with secure, cryptographically strong tokens such as OAuth tokens or JWTs with proper signature validation. Implement strict server-side validation of all authorization credentials and ensure that authentication tokens cannot be easily decoded or manipulated. Introduce multi-factor authentication (MFA) to add an additional layer of security for user accounts. Conduct thorough security testing, including penetration testing and code reviews focused on authentication and access control. Users should be advised to update the app once a patch is released and to use strong, unique passwords. Organizations should monitor for suspicious account activity and implement anomaly detection to identify potential unauthorized access. Additionally, educating users about phishing and credential security can reduce the risk of attackers obtaining valid email addresses. Finally, maintain compliance with GDPR by promptly addressing breaches and notifying affected users if compromise occurs.