Browser extension permissions define what data and browser functions an extension can access, such as tabs, storage, or web requests. Broad permissions can let an extension inspect sensitive content, modify pages, or capture session data, which makes extension governance a security control rather than a usability issue.
Expanded Definition
Browser extension permissions are the browser-level authorisations that determine what an extension can see, read, change, or intercept across tabs, storage, downloads, cookies, and network requests. In NHI security, they matter because an extension often operates with delegated execution authority that can approximate a privileged agent if permissions are broad.
Definitions vary across vendors and browser ecosystems, but the security model is consistent: more permissions increase the extension’s ability to observe user and workload context, and therefore increase the blast radius if the extension is compromised. This is especially important when extensions interact with authentication flows, internal portals, or developer tooling. The OWASP Non-Human Identity Top 10 is useful here because it frames excess authority as an identity risk, not just an add-on concern. In practice, browser extension permissions should be reviewed the same way other NHI access paths are reviewed, with explicit attention to least privilege, data exposure, and session interception risk.
The most common misapplication is granting broad permissions during installation and treating them as harmless browser defaults, which occurs when teams approve extensions without validating the specific data paths they can reach.
Examples and Use Cases
Implementing browser extension permissions rigorously often introduces friction, requiring organisations to weigh user productivity against the operational risk of overbroad access.
- A developer extension that only needs syntax highlighting is also granted access to all sites, allowing it to inspect internal dashboards and authentication pages.
- A password manager extension requests read-and-write access to page content, which is necessary for autofill but should be constrained to trusted domains and vetted build provenance.
- A support or QA extension captures web requests for troubleshooting and accidentally exposes bearer tokens or cookies from production sessions, similar to patterns seen in the Hard-Coded Secrets in VSCode Extensions research.
- An automation extension with tabs and scripting permissions is used to move data between SaaS tools, but its access scope is never revisited after the workflow changes.
- Security teams compare extension scopes against browser policy baselines and NHI controls, using sources such as the Ultimate Guide to NHIs — Key Challenges and Risks and NIST SP 800-53 Rev 5 Security and Privacy Controls to justify periodic review.
Why It Matters in NHI Security
Browser extensions are often overlooked because they appear to be user productivity tools, yet they can function as hidden privileged intermediaries between people, SaaS applications, and sensitive secrets. That matters in NHI governance because extensions can read tokens from pages, observe session state, and alter browser behaviour in ways that resemble an embedded agent with tool access.
This risk is not theoretical. NHI Mgmt Group reports that 97% of NHIs carry excessive privileges, a pattern that maps directly to extension ecosystems when permissions are granted too broadly or never revisited. The same governance failures that drive exposed service accounts also appear in extension sprawl, where approvals outlive their business need. Teams should align extension review with least-privilege controls in the OWASP Non-Human Identity Top 10 and restrict access paths that can reach secrets, internal data, or session-bound workflows.
Organisations typically encounter the impact only after a token theft, page manipulation, or account compromise, at which point browser extension permissions become operationally unavoidable to address.
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 SP 800-53 Rev 5 set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| OWASP Non-Human Identity Top 10 | NHI-02 | Overbroad extension permissions create the same excess-authority risk as other NHIs. |
| NIST CSF 2.0 | PR.AA-1 | Extension access should be approved and bounded before it can touch sensitive resources. |
| NIST SP 800-53 Rev 5 | AC-6 | Least privilege control applies directly to extension capabilities and page access. |
Constrain extension permissions to the minimum functions required for the business need.
Related resources from NHI Mgmt Group
Deepen Your Knowledge
Reviewed and updated by the NHIMG editorial team on August 19, 2026.
NHI Mgmt Group — the #1 independent authority on Non-Human Identity, IAM, and Agentic AI security. nhimg.org
