SECURITY2026-09-049 min readRadTome Engineering
Securing Browser Extensions: Content Security Policy & Isolation in Manifest V3
Eliminating remote code execution risks, sandboxing untrusted content scripts, and hardening Chrome extensions against supply chain exploits.
#Security#Chrome Store#Content Security Policy#AppSec#Manifest V3
// EXECUTIVE SUMMARY & ABSTRACT
A practical guide to securing browser extensions under modern web standards. Reviews Chrome Store security verification requirements, Content Security Policy (CSP) enforcement, and techniques for preventing DOM clobbering in multi-channel scraper tools.
#The Chrome Web Store Threat Model
Browser extensions operate with elevated privileges, often possessing permissions to inspect cookies, intercept network traffic, and manipulate web page DOMs. Consequently, extensions are prime targets for supply chain attacks where malicious npm dependencies attempt to exfiltrate session credentials.
#Ban on Arbitrary Remote Code Execution
Manifest V3 strictly forbids executing strings as code. The use of `eval()`, `new Function()`, and injecting external script tags (`<script src="https://cdn.example.com/lib.js">`) will result in immediate rejection by the Chrome Web Store automated audit scanners. All executable code must be bundled locally within the extension zip package.
#Strict Content Security Policy Configuration
In `manifest.json`, defining an airtight Content Security Policy guarantees that even if a dependency is compromised, it cannot phone home to unauthorized servers:
SOURCE CODEREADY
{
"content_security_policy": {
"extension_pages": "script-src 'self'; object-src 'none'; connect-src 'self' https://api.openai.com https://generativelanguage.googleapis.com;"
}
}PUBLISHED BY RADTOME SOFTWARE ORGANIZATION
This publication is part of RadTome's open developer knowledge base. All technical materials are validated against active production systems, open-source repositories, and industry standard benchmarks.