CVE-2025-27426

What it actually does

A server-side redirect from a malicious site to an internal error page allows the browser to display a spoofed URL in the address bar, enabling URL spoofing.

Why it matters to the business

Users may be tricked into visiting phishing or malicious sites under the false impression they are on legitimate domains, increasing risk of credential theft or malware exposure across iOS Firefox deployments.

How an attack unfolds

An attacker hosts a malicious site that performs a server-side redirect to an internal error page; when a victim visits via Firefox for iOS, the browser displays the spoofed URL, allowing phishing or social engineering without client-side indicators of the redirect.

How to fix it

Upgrade Firefox for iOS to version 136 or later on all affected devices; verify the update through the App Store and confirm the version in browser settings.

How to confirm the fix worked

Confirm installed version is 136 or higher via browser about screen; test with known redirect payloads to ensure spoofed URLs no longer appear; review enterprise mobile device management policies for enforced updates.

Typical attack path

1. Attacker registers or compromises a domain and configures server-side redirect to an internal error page URL
2. Attacker crafts a link or lures victim to the malicious site via email, messaging, or web content
3. Victim opens the link in Firefox for iOS, triggering the redirect
4. Browser displays the spoofed URL, enabling further social engineering or credential harvesting

How to detect it

Review browser history and crash logs for unexpected redirects to error pages; correlate with network logs showing server-side redirects from untrusted domains; no widespread exploitation artifacts are documented.

What your security team should do

• Prioritize deployment of Firefox for iOS 136+ across all managed iOS devices within 30 days
• Update mobile application management policies to block older vulnerable versions
• Educate users on verifying URLs independently of the address bar for sensitive actions
• Monitor for increased phishing reports targeting iOS Firefox users