Mdaemon Webmail Cross-site Scripting

Authenticated stored cross-site scripting (XSS) in the contact name field in the distribution list of MDaemon webmail 19.5.5 allows an attacker to executes code and perform a XSS attack while opening a contact list. (2021-02-03, CVE-2020-18724)

Stored cross-site scripting (XSS) in file attachment field in MDaemon webmail 19.5.5 allows an attacker to execute code on the email recipient side while forwarding an email to perform potentially malicious activities. (2021-02-03, CVE-2020-18723)

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>