browser-extension-developer

Prompt injection protection evaluates user inputs within a Chrome Manifest v3 extension using a 3-branch parallel detection architecture integrated with webhook proxy validation. The extension intercepts prompts client-side, applies threat scoring, and returns ALLOW, SANITIZE, or BLOCK decisions to enforce security in the UI before submission.

Manifest v3 is Chrome's current extension framework that replaces content scripts with a background service worker and enforces stricter security policies. It's required for modern Chrome extensions and enables secure webhook integration, debugging hooks, and client-side processing logic like prompt validation.

Yes. Content scripts inject into web pages to intercept user input, while a background service worker manages webhook communication, threat detection logic, and decision enforcement. This architecture enables real-time prompt evaluation and browser fingerprinting across client and background layers.

Configure the webhook proxy endpoint in your extension's background service worker to receive intercepted prompts from content scripts. The webhook applies 3-branch detection logic and returns threat scores, PII detection flags, and arbiter decisions that the extension enforces as ALLOW, SANITIZE, or BLOCK actions.

The extension includes built-in testing hooks and a dedicated UI for debugging. Load the unpacked extension in Chrome's developer mode to inspect content script execution, webhook responses, threat scores, and branch detection results in real time before production deployment.

Yes. The 3-branch detection system identifies PII within intercepted prompts and returns a pii_detected flag alongside sanitized input and threat scoring. Browser fingerprinting and parallel branch analysis refine detection accuracy to reduce false positives.