Best Practices for Developing a Secure Extension and Protecting User Data
When developing a Chrome extension, it is crucial to follow best practices to ensure the security of user data and protect the privacy of users. This guide will provide you with recommendations and examples for developing a secure extension using the project available at https://github.com/screenly/chrome-extension/.
1. Minimize Permissions
Only request the permissions your extension needs to function. Unnecessary permissions can expose user data and increase the attack surface.
For example, in the manifest.json file, request only the permissions your extension requires:
"permissions": [
"activeTab",
"storage",
"tabs"
]
2. Content Security Policy (CSP)
Use a Content Security Policy (CSP) to prevent cross-site scripting (XSS) attacks and other code injection vulnerabilities. The CSP specifies the domains that the browser should consider as valid sources of executable scripts.
In the manifest.json file, include a content_security_policy property:
"content_security_policy": "script-src 'self' https://trusted-site.com; object-src 'self'"
3. Secure Communication
Use HTTPS for all communication between the extension and web services. This ensures that data transmitted between the extension and servers is encrypted and protected from eavesdropping.
For example, in the content.js file, use fetch with an HTTPS URL:
fetch('https://api.trusted-site.com/data')
.then(response => response.json())
.then(data => console.log(data));
4. Data Storage
Store sensitive user data securely. Use the Chrome storage API to store data in an encrypted format. Avoid storing sensitive data in local storage or cookies, as this data can be accessed by other extensions or JavaScript code running on the page.
For example, in the background.js file, use the chrome.storage API to store data:
chrome.storage.local.set({ key: value }, function() {
console.log('Value is set to ' + value);
});
5. Regular Updates
Keep your extension up-to-date with the latest security patches and bug fixes. Regularly review and update your extension’s codebase to ensure it follows the latest best practices and security guidelines.
For example, when a security vulnerability is discovered in a dependency, update the dependency to a secure version:
"dependencies": {
"lodash": "^4.17.21"
}
6. Code Quality
Maintain high code quality by following coding standards, using linters, and writing unit tests. High-quality code is easier to maintain, review, and secure.
For example, in the package.json file, include eslint and jest for linting and testing:
"devDependencies": {
"@babel/core": "^7.14.6",
"@babel/preset-env": "^7.14.7",
"babel-jest": "^26.6.3",
"eslint": "^7.28.0",
"jest": "^26.6.3"
}
7. User Onboarding
Provide clear instructions and contextual help within the extension to ensure that first-time users can understand its value-add and adopt it easily.
For example, in the popup.html file, include a welcome message and a link to the documentation:
<!DOCTYPE html>
<html>
<body>
<h1>Welcome to the Screenly Extension!</h1>
<p>
For more information and setup instructions, please visit our
<a href="https://screenly.github.io/chrome-extension/" target="_blank"
>documentation</a
>.
</p>
</body>
</html>
By following these best practices, you can develop a secure Chrome extension that protects user data and maintains the privacy of users.
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