During a security research I found an authenticated Stored XSS vulnerability.

The name of the plugin is: Donation Thermometer < 2.1.3

Description

The plugin does not sanitise and escape some of its settings, which could allow 
high privilege users such as admin to perform Stored Cross-Site Scripting 
attacks even when the unfiltered_html capability is disallowed 
(for example in multisite setup)

POC

Put the following payload in the Settings > Thermometer > Currency settings: 

" style=animation-name:rotation onanimationstart=alert(/XSS/)//

Save the changes, the XSS will be triggered when accessing the 
settings again, as well as in the frontend in pages 
where the [thermometer] is embed.

Additional information

WPSCAN link: https://wpscan.com/vulnerability/97201998-1859-4428-9b81-9c2748806cf4

Plugin has more than 3,000+ active installations.