The YaySMTP and Email Logs: Amazon SES, SendGrid, Outlook, Mailgun, Brevo, Google and Any SMTP Service plugin for WordPress is vulnerable to Stored Cross-Site Scripting in versions 2.4.9 to 2.6.2 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. Note: The vulnerability has been initially patched in version 2.4.8 and was reintroduced in version 2.4.9 with the removal of the wpksespost() built-in WordPress sanitization function.

The YaySMTP WordPress plugin before 2.2.2 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 when the unfilteredhtml capability is disallowed (for example in multisite setup)

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.

The YaySMTP WordPress plugin before 2.2.1 does not have capability check in an AJAX action, allowing any logged in users, such as subscriber to view the Logs of the plugin

The YaySMTP WordPress plugin before 2.2.1 does not have capability check before displaying the Mailer Credentials in JS code for the settings, allowing any authenticated users, such as subscriber to retrieve them