CVE-2026-13356 Firefox for iOS vulnerability
A malicious webpage could interrupt a pending navigation by enqueuing a synchronous JavaScript dialog, causing the browser UI to display the destination origin in the address bar while continuing to render attacker-controlled content. This vulnerability was fixed in Firefox for iOS 152.3.
Quick answer
Firefox for iOS should be reviewed and updated if it matches the affected versions. The recommended fix is to apply the vendor-supported patched version or the mitigation steps below, then retest the public website with Fixnx.
Who is affected
Affected versions
- Firefox for iOS before 152.3
Fixed versions
- 152.3
How to fix it
CVE-2026-13356 affects Firefox for iOS where a malicious webpage can interrupt pending navigation with a synchronous JavaScript dialog, causing Firefox for iOS to show the destination origin while still rendering attacker-controlled content. Prioritize managed iOS fleets, users who handle sensitive web sessions, and environments where mobile browser origin trust is important. Mozilla fixed the issue in Firefox for iOS 152.3. Use MDM, App Store management, or user update guidance to ensure all devices run the fixed version or later.
- Inventory managed and unmanaged iOS devices that use Firefox for iOS for business, administrative, or sensitive browsing workflows.
- Identify Firefox for iOS versions before 152.3 and schedule an update to Firefox for iOS 152.3 or later.
- Deploy the update through MDM or App Store management, and communicate manual update instructions to unmanaged users where needed.
- Temporarily advise users to avoid trusting address-bar state after interrupted navigations or JavaScript dialog prompts until updated.
- Review mobile management logs, app inventory, and support tickets for signs of delayed updates or suspicious origin-spoofing reports.
- Prioritize updates for privileged users, administrators, finance users, and anyone who accesses sensitive web applications from iOS devices.
- If credential phishing is suspected, revoke sessions, rotate affected credentials, and preserve browser or identity-provider evidence where available.
Scan now. Google sign-in is only needed to unlock fix guidance.
Verify the fix
- Confirm MDM inventory, App Store records, or device checks show Firefox for iOS 152.3 or later on affected iOS devices.
- Confirm managed iOS devices report Firefox for iOS 152.3 or later and navigation/dialog spoofing test pages no longer misrepresent the address bar origin.
- Confirm users can no longer reproduce origin spoofing with interrupted navigation and synchronous dialog behavior on the patched app.
- Review identity-provider logs for suspicious mobile browser sign-ins before and after the update.
- Document rollout coverage, exceptions, user notification, and evidence retained for the change record.
Related categories
Trusted references
FAQ
What is affected by CVE-2026-13356?
Firefox for iOS versions listed as affected should be reviewed: Firefox for iOS before 152.3.
What should I fix first?
Start with internet-facing sites, admin panels, login flows, plugins, themes, modules, packages, and systems that process user-controlled input or sensitive data.
How do I confirm the fix worked?
Apply the patched version or mitigation, clear caches where relevant, retest the affected workflow, and run a new Fixnx scan to verify public website exposure signals.
How are Fixnx security risk categories chosen?
Fixnx keeps one canonical risk page and assigns only broad, relevant categories such as ecosystem, technology area, or vulnerability class.