let history = {}; browser.webRequest.onResponseStarted.addListener(i => { if (i.statusCode == 403) { let iFQDN = (new URL(i.url)).hostname; let iServer = 'Unknown'; i.responseHeaders.forEach(x => { if (x.name == 'Server') { iServer = x.value; } }); let iDate = (new Date()).toUTCString(); history[iFQDN] = [i.url, iServer, iDate]; } return; }, { urls: ['http://*/*', 'https://*/*'], types: ['main_frame'] }, ['responseHeaders']); browser.runtime.onMessage.addListener((request, sender, sendResponse) => { if (request && sender) { if (request == 'get') { sendResponse(history); } if (request == 'clear') { history = {}; sendResponse(true); } } });