WordPress Plugin Simple Post 1.1 - 'Text field' Stored Cross-Site Scripting (XSS)

# Exploit Title: WordPress Plugin Simple Post 1.1 - 'Text field' Stored Cross-Site Scripting (XSS)
# Date: 23/07/2021
# Exploit Author: Vikas Srivastava
# Software Link: https://wordpress.org/plugins/simple-post/
# Version: 1.1
# Category: Web Application
# Tested on Mac

How to Reproduce this Vulnerability:

1. Install WordPress 5.7.2
2. Install and activate Simple Post
3. Navigate to Settings >> Simple Post and enter the XSS payload into the Text input field.
4. Click Update Options.
5. You will observe that the payload successfully got stored into the database and when you are triggering the same functionality at that time JavaScript payload is executing successfully and we are getting a pop-up.
6. Payload Used: "><script>alert(document.cookie)</script>