Input validation vulnerability in Back To The Top Button 2.1.5

The Back To The Top Button plugin for WordPress has a security flaw that could allow someone with administrator-level access to inject malicious web scripts into pages on websites using the plugin. This would cause the malicious script to run on the page whenever a user visits the page. This security flaw only affects websites using the plugin that are installed on multiple sites or websites where a security setting called unfiltered_html has been disabled.