Skip to main content

IE is really unsafe?

Is IE unsafe? I tend to conclude so, regarding my interactions with Giorgio on an issue of XSS in Paypal. This is because the flaw in IE that it doesn't encode the URL before sending it on the wire.
While interacting with Giorgio I came across something new to me: InputDecoding. As Giorgio says:
@Nilesh:
In the Paypal case, it’s not doing output encoding, it’s skipping input decoding (quite strangely).
The correct workflow should be:
  1. Input decoding (decodeURIComponent)
  2. Input validation
  3. Output with output-specific (HTML or JavaScript) encoding

This Paypal page was missing all the 3, and only by luck the fact browsers different by IE properly encode the URL saves them from XSS.

The InputDecoding as far as I can understand is the process of getting back the URLencoded input in original form so that application can understand it properly and exeute it. After executing the application once again must escpae the output in proper manner (HTML escape or Javascript escape).

Again, regarding IE Giorgio said:

@Nilesh:

>>IE doesn’t encode the URL?

No it doesn’t. Therefore an application which doesn’t encode its output is not protected even if it doesn’t decode the input.
You should always encode the output, and decode the input if it makes sense (almost always).

>>IS there any way to bypass this URL-encoding and execute XSS?

No (except in IE), unless the injection point is not quoted, because quotes in an URL are usually escaped by the browser (except in IE).

So, I became more susceptible towards IE. I know it since long back that IE is comparatively unsafe when I was testing script in file upload in Google Pages. The Firefox simply printed the URL back whereas IE executed the script. Other theories as well goes against the IE.

Even in case of above Paypal case , exploitation of this specific Paypal vulnerability requires the “double quotes” character to pass through with no encoding: therefore, while the vast majority of XSS exploits are cross-browser, this one affects exclusively IE.




Comments

Post a Comment

Popular posts from this blog

Using an AirPcap device in Windows with Wireshark

Capturing wireless traffic in a Windows environment is unfortunately not as easy as a setting change. As with most Windows-based software, drivers in Windows are often not open source and do not allow for configuration change into monitor mode. With this in mind, we must use a specialized piece of hardware known as an AirPcap device. Once you have obtained an AirPcap device you will be required to install the software on the accompanying CD to your analysis computer. The configurable options include: • Interface - Select the device you are using for your capture here. Some advanced analysis scenarios may require you to use more than one AirPcap device to sniff simultaneously on multiple channels. • Blink LED - Clicking this button will make the LED lights on the AirPcap device blink. This is primarily used to identify the specific adapter you are using if you are using multiple AirPcap devices. • Channel - In this field, you select the channel you want AirPcap to listen on. Extension C...
5 comments
Read more

Anti CSRF header

Recently I came across an application which was preventing crsf attacks using a unique non-traditional approach. In traditional approach the csrf is thwarted by embedding unique random tokens, called nonce, in each sensitive page. But this application, which was making ajax calls and used jQuery, was creating a header to identify the valid and invalid requests altogether. The idea is to generate a custom header, x-session-token in this case, with every request which is considered sensitive and includes any sort of transaction. For example: xhr.setRequestHeader('x-session-token', csrf_token)   At the server level, server checks for this header if found request is fulfilled, otherwise rejected. We need to use xhr calls for making use of this technique, not useful in regular POST and GET requests. Since, I was not aware of this kind of countermeasures, probably, since most of the applications I did were using standard requests. So, I searched a bit and found even Go...
4 comments
Read more

Some one watching where you visited!

Yes... Mozilla has been susceptible to browser-history stealing java script code. Today, Giorgio posted some cool information about the exploit. Mozilla is already working on this. This bug has been reported. Actually they have set up a web site to show the proof-of-concept. Visit www.statrpanic.com in FF,Safari or Netscape and it will tell you which websites have you been already ! But I am not sure it will work in IE or not because my IE is not responding to the website. Clearing history of visited website makes you safe to this attack. I mean this is one way..may be there are other ways to exploit this. But I have found this effective. Try it yourself in FF and then in IE and see the results.
Post a Comment
Read more