Missing Authorization vulnerability in Saad Iqbal Post SMTP post-smtp allows Exploiting Incorrectly Configured Access Control Security Levels.This issue affects Post SMTP: from n/a through <= 2.9.11.

The Post SMTP plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the from and subject parameter in all versions up to, and including, 3.0.2 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.

The Post SMTP – Complete Email Deliverability and SMTP Solution with Email Logs, Alerts, Backup SMTP & Mobile App plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'useremail' parameter in all versions up to, and including, 4.0.1 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. This is exploitable without authentication on WordPress Multisite installations with public registration enabled, as WordPress accepts email addresses containing numeric HTML character references that Post SMTP's stricter validator rejects, persisting the attacker-controlled address verbatim to the email log via the failed-send exception message.

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in Post SMTP POST SMTP allows Reflected XSS.This issue affects POST SMTP: from n/a through 2.8.6.

The Post SMTP plugin for WordPress is vulnerable to authorization bypass in all versions up to, and including, 3.6.1. This is due to the plugin not properly verifying that a user is authorized to update OAuth tokens on the 'handlegmailoauthredirect' function. This makes it possible for authenticated attackers, with subscriber level access and above, to inject invalid or attacker-controlled OAuth credentials.

The Post SMTP plugin for WordPress is vulnerable to generic SQL Injection via the ‘columns’ parameter in all versions up to, and including, 3.1.2 due to insufficient escaping on the user supplied parameter and lack of sufficient preparation on the existing SQL query. This makes it possible for authenticated attackers, with Administrator-level access and above, to append additional SQL queries into already existing queries that can be used to extract sensitive information from the database.