Simple Event Planner Cross-site Scripting

Authenticated Stored Cross-Site Scripting (XSS) in Simple Event Planner plugin <= 1.5.4 allows attackers with contributor or higher user roles to inject the malicious script by using vulnerable parameter &custom[add_seg][]. (2022-03-25, CVE-2022-25611)

Multiple Authenticated Persistent Cross-Site Scripting (XSS) vulnerabilities in Simple Event Planner WordPress plugin <= 1.5.4 allows user with author or higher user rights inject the malicious code via vulnerable parameters: &custom[event_organiser], &custom[organiser_email], &custom[organiser_contact]. (2022-03-25, CVE-2022-25612)

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>