Description

The Convos is an open source multi-user chat that runs in a web browser. Characters starting with "https://" in the chat window create <a> tag. Stored XSS vulnerability using onfocus and autofocus occurs because escaping exists for "<" or ">" but escaping for double quarter does not exist.

Proof of Concept

Username : whwjddnjs142@gmail.com
Password : qwer12211@

1. Open the https://demo.convos.chat/login and Login as to above account
2. Go to https://demo.convos.chat/chat/irc-demo-irc-convos/<chat room name>
3. In chat room. Enter the https://x."//onfocus="alert(document.domain)"//autofocus="" b="

Video : https://www.youtube.com/watch?v=L1Be-D-GVmQ

Impact

Through this vulnerability, an attacker is capable to execute malicious scripts.