Monday, January 8, 2018

Pagespeed ultimate

To bypass Google Pagespeed insight warning with the images on your site, there are some ways. 1st is don't use any image, easy!. 2nd is Image Compression and...:
- Image compression is not enought
- Image compression + Sampling factor(ref:…/Compression/JPEG/J5mods2007.pdf , at: "Down-Sampling"). Okay now Google Pagespeed insight won't warn you about the images on your site. But for the best =>
- Try to use compression + sampling factor AND use PJPEG(Progressgive JPG)- PJPEG is believed to reduce 2-10% file size comparing to standard JPEG. Some big names are using PJPEG Facebook(trên iOS), Twitter, Pinterest...
Vietnamese big name: VnExpress just a small amount, those may come from accidents while editing images. Dantri small amount, not from direct site, Ads! Tiki Full Progressive image, Lazada small amount!


Next will be the collect of how the size of the site is a huge problem!!!

Saturday, March 8, 2014

UPlayback using nodejs first draft



Tuesday, March 4, 2014

Javascript and the pain of browsers!


1. Javascript File Loading
Load script basic:
Load file in header, middle

Load file in bottom:

Load script dynamically:

Insert DOM Element:
                  By using dynamic js file loading you can avoid the other files being blocked while the js file is downloading, so maximize total number of js files can be requested at a time.
ga.js without dynamic load

ga.js with dynamic load

In the first case, GA use: document.write(unescape("%3Cscript src='" + gaJsHost + "' type='text/javascript'%3E%3C/script%3E")); it blocks other request until ga.js completely loaded.
In the dynamic loading case:
  var _gaq = _gaq || [];
  _gaq.push(['_setAccount', 'UA-7345054-1']);
  (function() {
    var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true;
    ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '';
    var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s);
The command being pushed in to queue until ga.js fully loaded and create a DOM element with source pointed to ga.js destination.
The dynamic loading, there is only execution period is on browser UI Thread, so it decrease the UI Blocking which cause other UI Thread have to wait. Notice that in this case, code execution will be executed right before the next UI Thread fired!

Defer :
                  With defer tag, browser wont execute script until every UI content updated successfully!
                  Cons: Compatible with IE, the other one are not supported in older versions!

Script execution is fired at end, after UI updated.

Async :
                  Js file will be downloaded and parsed immediately but will be executed when it is executable on UI Thread, a little similar to dynamic loading!

Compress javascript file:


2. Value & Execute
Local, global variables

Scope chain :
Keep in mind, try to limit the global variables as much as possible, in scope chain JavaScript always put global variables at end. So every executions, JavaScript engine have to spend more effort and time to look for the global variables! The local variables are always on the first scope! Also, global variables are easy overwritten by accident.
Global variable access
n=0; m=0;

=> ~18ms
Local access, global cache
var n=0, m=0;
for(var i=0;i<=9999;i++){

=> ~2ms

Scope chain map:

try/catch, with agumentation:
Execute script with this method, local variable will be pushed into 2nd scope, try/catch or with agument will be in the first scope, so accessing to the variables takes more time.

While executing script, JavaScript engine will search through scope chain to find the object ‘name’, stat from the first scope, if nothing found it will continue to search to the next scope until end. If there is no object found in the whole scope then it will return undefined. Oh hey, reduce the Object deep.

Loops (ECMA-262 – Chap 12-6)
for loop : 4 parts– Pretest, condition, post-execute and loop body
while : 2 parts – Simple pretest loop, prestest evaluated excuted and loop body followed.
do-while : 2 parts – Post-test loop, loop body and post-test condition.
for-in :
Avoid to work with array by using for-in, the working process of this function is it will go through all of the items and return the properties of the items but not follow by the index.
for-in slowest!!!
var person={fname:"Ho",lname:"Ten",age:25}, cnt='';
for(var j=0;j<1000 br="" j="">     for (var z in person)
        cnt += person[z] + j + '|';

=> ~1ms
var person={fname:"Ho",lname:"Ten",age:25}, cnt='';
for(var j=0;j<1000 br="" j="">     for(var i=0;i<1 br="" i="">          cnt += person['fname'] + j + '|' + person['lname'] + '|' + person['age'] + '|';

=> ~1ms

3. DOM
DOM access
HTML Collection is similar to array, it always updated so while being updated, DOM always re-painted/re-flow(read below about this) after each execution. So to reduce the access, execution time: Cache HTML Collection into local variable (include length, items…)
Cache DOM in local variable.
    document.getElementById('toc__header').innerHTML='Table of Contents ' +i;

var doc = document.getElementById('toc__header').innerHTML='Table of Contents ';
    doc + i;


DOM Element change:
Re-paint : When there is a style changed(Include background, color, border).
Re-flow : When there is a changed of structure, shape… Once re-flow event triggered, JavaScript engine will have to work with all of the elements which relate to the current one, it is highly chance that the first DOM element also being affeted. SO – RE-FLOW IS REALLY SLOW.

Remove element, update the change and insert into the previous position.
Set element to none, update the change and set it display back.
Use documentFragment  to change the DOM Element to reduce repain, reflow.
To change element’s style, just use the css and change the class name.

Long running scripts:

This issue happens difference on each browsers.
On IE Javascript engine will warns the error depends on the total of executed command, default is 5.000.000. JS Engine will stop execute script while displaying the warn message, if you choose Yes, then the total of execution script number will be reset.
On Firefox Javascript engine warn the error depends on total execution time of the script, default is 10s. If Yes pressed, then total execution time will be reset.
Chrome does not work with the two of above methods, it depends on OutOfMemory event.
What may cause the Long running script issue:
- Working too much with DOM.
- Too much loop, or too much processes inside the loop.
- Too much recursion.

- Split task, data smaller:
var arr = [ "item1", "item2", "item3",…],
    carr = arr.concat();  //clone the array
chunk(carr, function(item){
    console. log(item);

- Use the setTimeout function to delay the script execution while process the other one:
            script to execute here…
        }, 100);

Javascript Memory Leaks:
Javascript has its Garbage Collector. Each object saved in memory and managed by the collector (store, withdraw) depends on if it still relates to the other objects or not. In some cases Garbage Collector lose its control, or the related objecte(s) in ‘circular reference’ then memory leaks happens. This issue is easy to happen when using with closure(inner) function to work with Object, DOM, Mouse event, Page event.
Reduce? :
Try to reduce using closure.
Attach specific event
Set Null to the object once finished working on it.

Others stuff:
Object literal:
Classic: var arr=new Array; var obj = new Object;
Literal: var arr = []; var obj={};
Classic way
for(var i=0;i<=999;i++){
var arr=new Array;
var obj=new Object;

for(var i=0;i<=999;i++){
var arr=[];
var obj={};

Try to get away with eval  cause each execution, JavaScript Engine will have to convert source code into executable before executing it.
Use function name when using setTimeout or setInterval function, if the script execute the function by passing the string, eg: ‘funcExam()’ then it becomes similar like eval():

Gzip : gzip scripts, stylesheets, XML, JSON (not images, PDF)

Minimum HTTP Request : To avoid blocking other resource requests, reduce UI blocking. Reduce cookie, Cookie is not cache able and always fresh on both client and server, so each cookie costs: Bandwidth, Computer/Server environment such as memory, cpu...

HTTP Header cache option:

Thursday, February 27, 2014 and Facebook likejacking

Share/Bookmark, a Vietnamese startup invested by CyberAgent Ventures last year (

I am watching around and noticed that they are doing shit-trick called facebook likejacking as the screenshot below:

A POST request to facebook will be generated when you click the close button at the top-right corner.
It was blocked by my antivirus, sorry foody!

Look into the detail header of this request:

Request URL:
Request Headers CAUTION: Provisional headers are shown.

Content-Type: application/x-www-form-urlencoded



Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/33.0.1750.117 Safari/537.36

Form Data
fb_dtsg: AQDBhOAV
action: like
__user: 1117881115
__a: 1
__dyn: 7wfGbwKBAo
__req: 1
ttstamp: 265816866104796586
__rev: 1139153

So what happens behind that? The hidden like button is under the close button. By modifying css  it will appear:

Javascript function to check status of the current user to do their rat trick:
window.fbAsyncInit = function () {
        appId: "395614663835338",
        channelUrl: "",
        status: !0,
        cookie: !0,
        xfbml: !0,
        frictionlessRequests: !0
    }), $(function () {
        var a = $("#fbLike");
        a.length > 0 && FB.getLoginStatus(function (b) {
            if (b.status == "not_authorized" || b.status == "connected") {
                var c = $.cookie("fbCookie");
                c ? a.remove() : $(document).mousemove(function (b) {
                        left: b.pageX - 15 + "px",
                        top: b.pageY - 3 + "px"
                    }), $(document.activeElement).attr("id") == "fbIframe" && ($.cookie("fbCookie", "1", {
                        expires: 5,
                        path: "/"
                    }), $.cookie("fbPro", provinceId || 217), a.remove())
You can see the detail source here:
Backup code: public.core.min.js_part1 , public.core.min.js_part2
At this time, foody's facebook page has more than 240k like, how many of them are real;)

//After the basic review above, now we can take a deeper inside the real likejacking of
See the video pls ;)... Dog tail appears soon!

Friday, February 21, 2014

Penetration Testing Addons For Firefox Browser


The majority of the penetration testers are using the Mozilla Firefox as a web browser for their pentest activities.This article will introduce the firefox addons that can be used for a web application penetration test.

1) Firebug

It is useful for the debugging tools that can help you tracking rogue javascript code on servers.

2) User Agent Switcher

You can use this extension to change the user agent of your browser.Useful for web application penetration tests that you want to check and the mobile versions of the websites.

3) Hackbar

Useful for SQL injection and XSS attacks.It includes also tools for URL and HEX encoding/decoding and many more.

4) HttpFox

Monitor and analyze all the incoming and outgoing HTTP traffic between your browser and the web server.

5) Live HTTP Headers

View the HTTP headers of a website instantly.

6) Tamper Data

View and modify HTTP/HTTPS headers and post parameters.

7) ShowIP

Shows the IP of the current page in the status bar.It also includes information like the hostname,the ISP,the country and the city.


Open Source Vulnerability Database Search.

9) Packet Storm search plugin

Search the packet storm database for exploits,tools and advisories.

10) Offsec Exploit-db Search

Search the Exploit-db archive.

11) Security Focus Vulnerabilities Search Plugin

Search for vulnerabilities in the Security Focus

12) Cookie Watcher

Watch the selected cookie in the status bar.

13) Header Spy

Shows HTTP Headers on status bar

14) Groundspeed

Manipulate the application user interface.

15) CipherFox

Displays the current SSL/TLS cipher and certificate on the status bar.

16) XSS Me

Tool for testing reflected XSS vulnerabilities.

17) SQL Inject Me

Extension to test SQL Injection vulnerabilities.

18) Wappalyzer

Discover technologies and applications that are used on websites.

19) Poster

Make HTTP requests,interact with web services and watch the output.

20) Javascript Deobfuscator

Show the JavaScript code that are running on web pages.

21) Modify Headers

Modify HTTP request headers.

22) FoxyProxy

Advanced proxy management tool.

23) FlagFox

Displays a country flag for the location of the web server.It also includes tools such as Whois,Geotool,Ping,Alexa etc.

24) Greasemonkey

Customize the way a webpage behaves by using small bits of JavaScript.

25) Domain Details

Displays Server Type, Headers, IP Address, Location Flag, and links to Whois Reports.

26) Websecurify

Useful for security assessments in web applications.

27) XSSed Search

Search the cross-site scripting database at XSSed.Com

28) ViewStatePeeker

ASP.NET viewstate viewer.

29) CryptoFox

CryptoFox is an encryption/decryption tool for cracking MD5 passwords.

30) WorldIP

Location of the web server,IP,Datacenter,Ping,Traceroute,RDNS,AS etc.

31) Server Spy

Unveils the technology of the web server (Apache, IIS etc.)

32) Default Passwords

Search default password database.

33) Snort IDS Rule Search

Search for Snort IDS Rules.

By pentestlab