CSP Evaluator Core Library

Introduction

Please note: this is not an official Google product.

CSP Evaluator allows developers and security experts to check if a Content Security Policy (CSP) serves as a strong mitigation against cross-site scripting attacks. It assists with the process of reviewing CSP policies, and helps identify subtle CSP bypasses which undermine the value of a policy. CSP Evaluator checks are based on a large-scale study and are aimed to help developers to harden their CSP and improve the security of their applications. This tool is provided only for the convenience of developers and Google provides no guarantees or warranties for this tool.

CSP Evaluator comes with a built-in list of common CSP allowlist bypasses which reduce the security of a policy. This list only contains popular bypasses and is by no means complete.

The CSP Evaluator library + frontend is deployed here: https://csp-evaluator.withgoogle.com/

Installing

This library is published to https://www.npmjs.com/package/csp_evaluator. You can install it via:

npm install csp_evaluator

Building

To build, run:

npm install && tsc --build

Testing

To run unit tests, run:

npm install && npm test

Example Usage

import {CspEvaluator} from "csp_evaluator/dist/evaluator.js";
import {CspParser} from "csp_evaluator/dist/parser.js";

const parsed = new CspParser("script-src https://google.com").csp;
console.log(new CspEvaluator(parsed).evaluate());