CVE-2024-9398

What it actually does

Allows an attacker to determine installed applications by inspecting results of window.open calls using specific protocol handlers.

Why it matters to the business

Enables environment fingerprinting that can facilitate targeted follow-on attacks against users, raising overall exposure in environments with high browser usage.

How an attack unfolds

An attacker serves a malicious webpage that invokes window.open with crafted protocol handlers and observes success or failure indicators to identify installed applications, potentially leveraging this in broader espionage or financial campaigns.

How to fix it

Upgrade affected Mozilla products to the fixed versions listed in the advisory; for github.com/argoproj/argo-cd/v2 update to 2.2.11 or later.

How to confirm the fix worked

Confirm browser and application versions meet or exceed the patched releases; test protocol handler behavior on updated builds to verify information is no longer leaked.

Typical attack path

1. Lure victim to attacker-controlled webpage
2. Trigger window.open calls with protocol-specific URIs
3. Analyze call results to detect presence of target applications
4. Use gathered intelligence to refine subsequent exploitation attempts

How to detect it

Review web server and browser logs for unusual sequences of window.open invocations or protocol handler tests; correlate with known threat actor patterns from listed campaigns.

What your security team should do

• Prioritize patching Firefox, ESR, and Thunderbird instances within the next 30 days given publication age
• Monitor for any related threat actor activity from espionage or financially motivated groups
• Review downstream dependents of listed packages for additional exposure