The YaySMTP WordPress plugin before 2.2.1 does not have proper authorisation when saving its settings, allowing users with a role as low as subscriber to change them, and use that to conduct Stored Cross-Site Scripting attack due to the lack of escaping in them as well.
https://wpscan.com/vulnerability/31405f1e-fc07-43f5-afc1-9cfbaf6911b7