CVE-2025-6428 is a security vulnerability identified in Mozilla Firefox for Android versions prior to 140. The flaw arises from the browser's improper handling of URLs embedded within a link's querystring parameter. Specifically, when a URL is provided as a parameter in a link, Firefox for Android erroneously follows the URL specified in the querystring rather than the legitimate URL intended by the link. This behavior can be exploited by attackers to redirect users to malicious websites without their knowledge, facilitating phishing attacks. The vulnerability is unique to the Android version of Firefox; desktop and other platform versions are unaffected. Although no known exploits are currently reported in the wild, the nature of the vulnerability—automatic redirection to potentially harmful URLs—poses a significant risk to user security and privacy. The absence of a CVSS score suggests that the vulnerability was recently disclosed and has not yet undergone formal severity assessment. The flaw impacts the confidentiality and integrity of user browsing sessions by enabling attackers to impersonate legitimate sites and potentially harvest sensitive information. Since the vulnerability does not require user authentication but does rely on user interaction (clicking a crafted link), it is exploitable in typical phishing scenarios. The scope is limited to Firefox for Android users running versions below 140, which may represent a substantial user base given Firefox's market share on Android devices. No official patches or mitigation links have been provided at the time of disclosure, emphasizing the need for immediate attention by users and organizations relying on Firefox for Android.

For European organizations, this vulnerability presents a tangible risk of phishing attacks targeting employees and customers using Firefox on Android devices. Successful exploitation could lead to credential theft, unauthorized access to corporate resources, and potential data breaches. Given the widespread use of mobile devices for accessing corporate email, intranet portals, and cloud services, attackers could leverage this flaw to bypass traditional email filtering and URL verification mechanisms by embedding malicious URLs within seemingly legitimate links. This could undermine trust in digital communications and lead to financial losses, reputational damage, and regulatory penalties under GDPR if personal data is compromised. Sectors with high mobile workforce usage, such as finance, healthcare, and government, are particularly vulnerable. Additionally, the vulnerability could be exploited in targeted spear-phishing campaigns against European organizations, especially those with employees who frequently use Firefox for Android. The lack of a patch at disclosure increases the window of exposure, necessitating proactive defensive measures.

1. Immediate user education campaigns should be conducted to raise awareness about the risk of clicking on suspicious links, especially those received via email or messaging apps on Android devices. 2. Organizations should enforce mobile device management (MDM) policies that restrict or monitor the use of Firefox for Android until a patch is available. 3. Encourage users to update Firefox for Android to version 140 or later as soon as Mozilla releases a fix. 4. Implement URL filtering and web proxy solutions that can analyze and block suspicious redirects originating from querystring parameters in URLs. 5. Deploy advanced email security gateways capable of detecting and quarantining phishing emails that exploit URL redirection techniques. 6. Consider alternative browsers on Android devices that are not affected by this vulnerability until a patch is released. 7. Monitor threat intelligence feeds for any emerging exploits targeting this vulnerability to enable rapid incident response. 8. For critical systems, enforce multi-factor authentication (MFA) to reduce the impact of credential compromise resulting from phishing.