Add security headers to the response

The following viewer response function adds several common security-related HTTP headers to the response. For more information, see the following pages on the MDN Web Docs website:

• Strict-Transport-Security

• Content-Security-Policy

• X-Content-Type-Options

• X-Frame-Options

• X-XSS-Protection

See this example on GitHub.

JavaScript runtime 2.0

async function handler(event) {
    const response = event.response;
    const headers = response.headers;

    // Set HTTP security headers
    // Since JavaScript doesn't allow for hyphens in variable names, we use the dict["key"] notation 
    headers['strict-transport-security'] = { value: 'max-age=63072000; includeSubdomains; preload'}; 
    headers['content-security-policy'] = { value: "default-src 'none'; img-src 'self'; script-src 'self'; style-src 'self'; object-src 'none'; frame-ancestors 'none'"}; 
    headers['x-content-type-options'] = { value: 'nosniff'}; 
    headers['x-frame-options'] = {value: 'DENY'}; 
    headers['x-xss-protection'] = {value: '1; mode=block'};
    headers['referrer-policy'] = {value: 'same-origin'};
    
    // Return the response to viewers 
    return response;
}

JavaScript runtime 1.0

function handler(event) {
    var response = event.response;
    var headers = response.headers;

    // Set HTTP security headers
    // Since JavaScript doesn't allow for hyphens in variable names, we use the dict["key"] notation 
    headers['strict-transport-security'] = { value: 'max-age=63072000; includeSubdomains; preload'}; 
    headers['content-security-policy'] = { value: "default-src 'none'; img-src 'self'; script-src 'self'; style-src 'self'; object-src 'none'"}; 
    headers['x-content-type-options'] = { value: 'nosniff'}; 
    headers['x-frame-options'] = {value: 'DENY'}; 
    headers['x-xss-protection'] = {value: '1; mode=block'}; 

    // Return the response to viewers 
    return response;
}