In this blog post I will discuss a XSS vulnerability I’ve found in AliExpress website.
I discovered this vulnerability while i bought items in the website, i wanted to contact with the seller so i sent him a message. As an application security expert i suspected that the messages system might be vulnerable to XSS so i started investigate it.
after a full investigation i found that it is possible to inject HTML <b> tag into the message, and it will be rendered as HTML code in the recipients' browser.
By injection the following malicious script payload in a message content parameter, the seller will browse to the message center in AliExpress website, thus, the malicious script will be executed on his browser:
Hello Seller :)<b style="position:fixed;top:0;left:0;display:block;width:100%;height:100%" onmouseover="alert('Barak Tawily, AppSec Labs')">PoC</b>
Note: the system doesn't allow send HTML tags in the content of the message, but it allows <b> tag only, thats why the payload to exploit the vulnerability is <b> tag and not any other.