Look for runtime actions, not just installation metadata. An extension is risky if it can change links, alter downloads, inject scripts, or trigger host execution in ways the user cannot easily see. Behavioural monitoring, managed deployment, and targeted review of update changes are stronger indicators than store ratings or permission counts.
Why This Matters for Security Teams
Browser extensions look harmless at install time, but the real risk appears when they run with access to pages, sessions, downloads, and user actions. A high permission count is not the same as high risk, and store ratings rarely reflect whether an extension can rewrite content, capture tokens, or chain into broader compromise. Current guidance suggests treating extensions as active software supply-chain components, not passive add-ons.
That matters because extension abuse often shows up as business impact before it shows up in traditional controls. NHIMG research on Ultimate Guide to NHIs — Why NHI Security Matters Now underscores why runtime identity and behaviour matter more than labels alone. For teams that manage browser access, the question is not whether an extension was approved once, but whether it can still act in ways the user did not intend. The NIST Cybersecurity Framework 2.0 is useful here because it pushes teams toward continuous monitoring and response rather than one-time trust decisions.
In practice, many security teams encounter extension abuse only after a session hijack, data exfiltration, or unauthorized script injection has already occurred, rather than through intentional review.
How It Works in Practice
Security teams should assess extensions by combining install-time review with runtime observation. The strongest signal is what the extension can actually do during a user session: change page content, redirect links, intercept form input, modify downloads, inject scripts, or call back to external services. Behavioural review is more reliable than permission counts because a small permission set can still be dangerous if it touches authentication flows or page DOM content.
A practical workflow usually includes managed deployment, allowlisting, targeted code review for updates, and telemetry on extension activity. The Top 10 NHI Issues highlights why credential handling, over-privilege, and weak monitoring remain recurring failure modes across non-human workloads. For browser extensions, the same pattern applies: once an extension can operate inside trusted browser sessions, it behaves like an identity-bearing workload and should be governed accordingly.
Teams often use the following checks:
- Does the extension alter what the user sees or downloads?
- Does it read or rewrite pages containing secrets, prompts, or payment data?
- Does an update introduce new hosts, new APIs, or new code paths?
- Can the extension trigger host execution, export data, or persist beyond user intent?
Where possible, map those behaviours to browser enterprise controls, policy-as-code review, and logging that can show when an extension acts outside expected bounds. The OWASP NHI Top 10 is especially relevant when extension behaviour crosses into agent-like autonomy, because tool use and hidden action chains create the same trust problem. These controls tend to break down in unmanaged BYOD browsers and consumer extension stores because security teams cannot reliably observe update provenance or runtime behaviour.
Common Variations and Edge Cases
Tighter extension control often increases user friction and support overhead, requiring organisations to balance safer browsing against productivity and compatibility. There is no universal standard for extension risk scoring yet, so best practice is evolving rather than settled.
Some extensions are low risk in a locked-down enterprise profile but high risk in a browser used for finance, HR, or source-code access. Others become risky only after an update, when the publisher adds remote code loading, new permissions, or a content script that touches sensitive pages. That is why targeted review of update diffs matters more than one-time approval. Security teams should also treat extensions that interact with identity providers, password managers, or download workflows as higher risk than their permission list suggests.
Another edge case is sanctioned productivity software that relies on broad browser access. In those environments, the right control is often segmented deployment rather than blanket removal. Current guidance suggests pairing allowlists with periodic behavioural review, because an extension that is safe today can become a hidden execution path tomorrow. For deeper NHI context, NHIMG’s 2024 ESG Report: Managing Non-Human Identities shows how often organisations still discover compromise only after damage is visible, reinforcing the need for runtime scrutiny over static trust.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
OWASP Non-Human Identity Top 10 address the attack and risk surface, while NIST CSF 2.0 and NIST AI RMF set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| OWASP Non-Human Identity Top 10 | NHI-03 | Extension updates and hidden actions create the same credential and trust risks as other NHIs. |
| NIST CSF 2.0 | DE.CM-7 | Continuous monitoring is essential for spotting risky extension behaviour after deployment. |
| NIST AI RMF | Risk decisions should account for dynamic behaviour, not only static approval metadata. |
Review extension behaviour as a living identity and revoke anything that exceeds approved runtime actions.
Related resources from NHI Mgmt Group
- How do security teams know if LiquidJS exposure is actually dangerous?
- How do security teams know if a Drupal SQL injection issue is actually under control?
- How do security teams know whether an NGINX deployment is exposed to this issue?
- How do security teams know whether a policy engine can be abused for cloud credential theft?
