Impact of reflected XSS attacks

[✨ Megiddo]

If an attacker can control a script that is executed in the victim's browser, then they can typically fully compromise that user. Amongst other things, the attacker can:

• Perform any action within the application that the user can perform.
• View any information that the user is able to view.
• Modify any information that the user is able to modify.
• Initiate interactions with other application users, including malicious attacks, that will appear to originate from the initial victim user.

There are various means by which an attacker might induce a victim user to make a request that they control, to deliver a reflected XSS attack. These include placing links on a website controlled by the attacker, or on another website that allows content to be generated, or by sending a link in an email, tweet or other message. The attack could be targeted directly against a known user, or could be an indiscriminate attack against any users of the application.

The need for an external delivery mechanism for the attack means that the impact of reflected XSS is generally less severe than stored XSS, where a self-contained attack can be delivered within the vulnerable application itself.