browser.webRequest.onHeadersReceived.addListener(info => {
const headers = info.responseHeaders; // original headers
console.log(headers);
for (let i=headers.length-1; i>=0; --i) {
let header = headers[i].name.toLowerCase();
if (header === "content-security-policy") { // csp header is found
// modifying media-src; this implies that the directive is already present
}
}
// return modified headers
return {responseHeaders: headers};
}, {
urls: [ "<all_urls>" ], // match all pages
types: [ "main_frame" ] // to focus only the main document of a tab
}, ["blocking", "responseHeaders"]);