Loading this script after after epub.js and it should overwrite the EPUBJS.core.request method. Change the login credentials in the file to your servers. USERNAME = 'abc' PASSWORD = 'xyz'

request_basicauth.js

USERNAME = 'abc'
PASSWORD = 'xyz'

EPUBJS.core.request = function(url, type) {
	var supportsURL = window.URL;
	var BLOB_RESPONSE = supportsURL ? "blob" : "arraybuffer";

	var deferred = new RSVP.defer();

	var xhr = new XMLHttpRequest();

	//-- Check from PDF.js: 
	//   https://github.com/mozilla/pdf.js/blob/master/web/compatibility.js
	var xhrPrototype = XMLHttpRequest.prototype;

	if (!('overrideMimeType' in xhrPrototype)) {
		// IE10 might have response, but not overrideMimeType
		Object.defineProperty(xhrPrototype, 'overrideMimeType', {
			value: function xmlHttpRequestOverrideMimeType(mimeType) {}
		});
	}

	xhr.open("GET", url, true, USERNAME, PASSWORD);
	xhr.onreadystatechange = handler;

	if(type == 'blob'){
		xhr.responseType = BLOB_RESPONSE;
	}

	if(type == "json") {
		xhr.setRequestHeader("Accept", "application/json");
	}

	if(type == 'xml') {
		xhr.overrideMimeType('text/xml');
	}

	xhr.send();

	function handler() {
		if (this.readyState === this.DONE) {
			if (this.status === 200 || this.responseXML ) { //-- Firefox is reporting 0 for blob urls
				var r;

				if(type == 'xml'){
					r = this.responseXML;
				}else
				if(type == 'json'){
					r = JSON.parse(this.response);
				}else
				if(type == 'blob'){

					if(supportsURL) {
						r = this.response;
					} else {
						//-- Safari doesn't support responseType blob, so create a blob from arraybuffer
						r = new Blob([this.response]);
					}

				}else{
					r = this.response;
				}

				deferred.resolve(r);
			} else {
				deferred.reject(this);
			}
		}
	}

	return deferred.promise;
};