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Cross-site Scripting occurrences in Engineers Online Portal
A Stored Cross Site Scripting (XSS) Vulneraibiilty exists in Sourcecodester Engineers Online Portal in PHP via the (1) Quiz title and (2) quiz description parameters to add_quiz.php. An attacker can leverage this vulnerability in order to run javascript commands on the web server surfers behalf, which can lead to cookie stealing and more. (2021-11-05, CVE-2021-42664)
Why Cross-site Scripting can be dangerous
Cross site scripting is an attack where a web page executes code that is injected by an adversary. It usually appears, when users input is presented. This attack can be used to impersonate a user, take over control of the session, or even steal API keys.
The attack can be executed e.g. when you application injects the request parameter directly into the HTML code of the page returned to the user:
https://server.com/confirmation?message=Transaction+Complete
what results in:
<span>Confirmation: Transaction Complete</span>
In that case the message can be modified to become a valid Javascript code, e.g.:
https://server.com/confirmation?message=<script>dangerous javascript code here</script>
and it will be executed locally by the user's browser with full access to the user's personal application/browser data:
<span>Confirmation: <script>dangerous javascript code here</script></span>