Browser Extension Malware Scanner

Browser extension malware scanner

Short answer

A browser extension malware scanner looks for static indicators such as remote script loading, dynamic code execution, obfuscation, credential access and suspicious endpoints. It cannot prove malware because it does not execute the extension or observe runtime behavior. Treat the result as a triage list, not a clean bill of health.

Drop an extension package hereor choose a file from your deviceChoose a fileSupported: CRX, XPI, ZIP, manifest.json. Maximum size: 25 MB.

Processed locallyCode is never executed

Your file stays in this browser. Parsing happens in a Web Worker; the extension code is read, never executed.

What the scan checks

Permissions, host access, content scripts, background scripts, CSP, externally_connectable, web-accessible resources, JavaScript patterns, referenced domains and risk categories.

MV3MV2CRXXPIZIPJSON

Static analysis shows references and patterns. It cannot prove that network activity happened or that an extension is malicious.

Compare two versions

See permission, domain and finding changes between two packages.

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Why the label is misleading

Malware detection usually combines signatures, reputation, runtime behavior and threat intelligence. A package analyzer can inspect the files, but it cannot see what happens after the extension loads, what a server returns or how the code behaves for a specific user.

That does not make static analysis useless. It is fast, private and good at finding capabilities and code patterns that deserve a closer look.

What static analysis can flag

Useful indicators include remote script references, eval-like calls, heavily obfuscated code, credential and cookie access, clipboard monitoring, crypto-mining patterns, raw IP endpoints and known temporary upload hosts.

Each indicator should be tied to a file, line and matched evidence. Without evidence, a scanner is asking you to trust a black box.

Remote code and dynamic execution
Obfuscation and unreadable bundles
Credential, cookie and clipboard access
Crypto-mining and exfiltration patterns
Suspicious endpoints and temporary upload hosts

How to use the result safely

Do not install an extension only because a static scan is clean. Do not remove a legitimate extension only because a bundled library triggered a rule. Read the evidence, check the publisher and compare versions when an update changes the risk profile.

For high-value accounts, use a separate browser profile with a minimal extension set and review permissions after every major update.

Frequently asked questions

Can a browser extension scanner detect malware?

It can detect static indicators associated with malicious behavior, but it cannot prove malware without runtime analysis and threat intelligence.

Is a free static scanner enough?

It is a useful first pass. Combine it with store review, publisher reputation, privacy policy review and runtime testing for high-risk cases.

Why do legitimate extensions trigger malware rules?

Bundled libraries, minification and legitimate sensitive features can match patterns that are also used by malicious code.

What should I do if a scan finds a critical indicator?

Read the evidence, check the publisher and release notes, and consider removing the extension until the behavior is explained.

Last reviewed: November 1, 2026