NavSentinel is a defensive browser extension. Its job is to make common navigation and credential-deception paths harder to execute quietly.

The most security-sensitive code lives in:

• extension/src/content/main_guard.ts
• extension/src/content/capture_isolated.ts
• extension/src/content/credential_guard.ts
• extension/src/shared/domain.ts
• extension/src/shared/storage.ts
• extension/src/sw/sw.ts

• extension-runtime relaying scoped to the current tab/frame
• explicit inbound message-type allowlists
• replayable blocked actions with short-lived ids
• no trust in arbitrary page-originated messages

• popup and redirect allowance windows are time-limited
• blocked actions expire quickly
• rollback exists as a recovery path for suspicious committed navigations
• allowlists are site-scoped rather than global

• password submits are intercepted before dispatch completes
• risky submits require explicit local user choice
• trusted domains are stored locally and scoped to registrable domains
• paste warnings discourage silent use of saved secrets on untrusted surfaces

• local-only storage
• bounded event log retention
• normalization and migration of older key shapes

• event logging is best-effort because chrome.storage.local is not transactional
• domain normalization uses a curated multipart-suffix list rather than the full PSL
• a browser extension cannot defend against a fully compromised browser or OS

If you find a security issue in the repository, report it privately to the maintainers before opening a public issue if the bug could materially weaken the extension's protections.

When reporting, include:

• affected file paths
• reproduction steps
• expected and actual behavior
• whether the issue affects navigation protection, credential protection, or both