[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"$fATb20QBdWccdeh72IsMtT26ZnDucAuNA9xMNz56eekk":3},{"lesson":4},{"id":5,"slug":6,"article_id":7,"title":8,"body":9,"prevention":10,"framework_refs":11,"status":23,"created_at":24,"published_at":25,"article":26,"tags":30,"podcasts":49},"dad09d51-9573-476e-885c-1455d53e49b4","malicious-firefox-extension-steals-google-session-cookies-via-deferred-payload","c22fe24a-7deb-4aa2-ae27-577a51a5e726","Malicious Firefox Extension Steals Google Session Cookies via Deferred Payload","A fraudulent Firefox browser extension disguised as a PDF identity verification tool targeted Portuguese- and Spanish-speaking users by fetching its malicious payload post-installation, effectively bypassing static code analysis at the time of submission or download. This 'living-off-the-land' technique — shipping clean code and loading malicious logic dynamically — is a growing tactic to evade extension store vetting and endpoint security tools. Once installed, the extension hijacked Google accounts by stealing session cookies and intercepting password reset values, granting attackers persistent account access without needing user credentials directly. This incident highlights the critical danger of unvetted third-party browser extensions as a supply chain attack vector, and underscores why user awareness about extension permissions and sources is essential.","**Immediate actions:**\n- Audit all installed browser extensions across your organization and remove any that are unrecognized, unnecessary, or sourced outside official stores.\n- Block or restrict the installation of browser extensions via Group Policy, MDM, or browser enterprise policies to approved allowlists only.\n\n**Long-term improvements:**\n- Implement a formal browser extension vetting process that includes dynamic\u002Fbehavioral analysis, not just static code review, before approving extensions for organizational use.\n- Enforce short-lived session tokens and hardware-based MFA (e.g., FIDO2) to limit the impact of session cookie theft on critical accounts like Google Workspace.\n- Educate users — especially those in targeted language regions — to verify the legitimacy of browser extensions before installation and to recognize social engineering lures.\n\n**Detection measures:**\n- Deploy endpoint detection tools capable of monitoring browser extension behavior, including unusual outbound network calls made by extensions after installation.\n- Enable logging and alerting on anomalous Google account session activity, such as logins from unexpected geolocations or simultaneous sessions, using tools like Google Workspace Alert Center or a SIEM.",[12,13,14,15,16,17,18,19,20,21,22],"CIS Control 2: Inventory and Control of Software Assets","CIS Control 4: Secure Configuration of Enterprise Assets and Software","CIS Control 14: Security Awareness and Skills Training","NIST SP 800-53 CM-7: Least Functionality","NIST SP 800-53 AC-17: Remote Access","NIST SP 800-53 SI-3: Malicious Code Protection","NIST SP 800-53 SC-28: Protection of Information at Rest (session tokens)","NIST CSF DE.CM-7: Monitoring for Unauthorized Activity","GDPR Article 32: Security of Processing (protecting user account data)","MITRE ATT&CK T1176: Browser Extensions","MITRE ATT&CK T1539: Steal Web Session Cookie","published","2026-09-24T00:20:42.81965+00:00","2026-09-24T00:20:42.508+00:00",{"id":7,"url":27,"slug":28,"title":29},"https:\u002F\u002Fsocket.dev\u002Fblog\u002Ffirefox-google-account-takeover?utm_medium=feed","malicious-firefox-extension-poses-as-pdf-identity-verifier-to-hijack-google-acco-06f42a","Malicious Firefox Extension Poses as PDF Identity Verifier to Hijack Google Accounts",[31,37,43],{"id":32,"name":33,"slug":34,"description":35,"color":36},"1ec88fde-2d0f-4ed8-932a-33f5ccc0fdc7","Access Control","access-control","Excessive privileges, missing MFA, weak auth","#f97316",{"id":38,"name":39,"slug":40,"description":41,"color":42},"7261eb8f-acd4-4d93-a489-7fdd652ec0ea","Security Awareness","security-awareness","Phishing, social engineering, human error","#22c55e",{"id":44,"name":45,"slug":46,"description":47,"color":48},"f0c2a0af-58aa-4128-87c9-6acd30f2dc48","Supply Chain","supply-chain","Third-party risk, compromised dependencies","#8b5cf6",[]]