The source code

    /*
    	Cookie Plug-in

    	This plug in automatically gets all the cookies for this site and adds them to the post_params.
    	Cookies are loaded only on initialization.  The refreshCookies function can be called to update the post_params.
    	The cookies will override any other post params with the same name.
    */

    var SWFUpload;
    if (typeof(SWFUpload) === "function") {
    	SWFUpload.prototype.initSettings = function (oldInitSettings) {
    		return function () {
    			if (typeof(oldInitSettings) === "function") {
    				oldInitSettings.call(this);
    			}

    			this.refreshCookies(false);	// The false parameter must be sent since SWFUpload has not initialzed at this point
    		};
    	}(SWFUpload.prototype.initSettings);

    	// refreshes the post_params and updates SWFUpload.  The sendToFlash parameters is optional and defaults to True
    	SWFUpload.prototype.refreshCookies = function (sendToFlash) {
    		if (sendToFlash === undefined) {
    			sendToFlash = true;
    		}
    		sendToFlash = !!sendToFlash;

    		// Get the post_params object
    		var postParams = this.settings.post_params;

    		// Get the cookies
    		var i, cookieArray = document.cookie.split(';'), caLength = cookieArray.length, c, eqIndex, name, value;
    		for (i = 0; i < caLength; i++) {
    			c = cookieArray[i];

    			// Left Trim spaces
    			while (c.charAt(0) === " ") {
    				c = c.substring(1, c.length);
    			}
    			eqIndex = c.indexOf("=");
    			if (eqIndex > 0) {
    				name = c.substring(0, eqIndex);
    				value = c.substring(eqIndex + 1);
    				postParams[name] = value;
    			}
    		}

    		if (sendToFlash) {
    			this.setPostParams(postParams);
    		}
    	};

    }