Is Post SMTP safe? Known vulnerabilities and latest version

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 'user_email' 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.

Missing Authorization vulnerability in WPExperts Post SMTP allows Exploiting Incorrectly Configured Access Control Security Levels. This issue affects Post SMTP: from 4.0.0 through beta.1.

Unauthenticated Cross Site Scripting (XSS) in Post SMTP <= 3.6.2 versions.

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 ‘event_type’ parameter in all versions up to, and including, 3.8.0 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 vulnerability is only exploitable when the Post SMTP Pro plugin is also installed and its Reporting and Tracking extension is enabled.

The Post SMTP plugin for WordPress is vulnerable to unauthorized modification of data due to a missing capability check on the `handle_office365_oauth_redirect()` function in all versions up to, and including, 3.8.0. This is due to the function being hooked to `admin_init` without any `current_user_can()` check or nonce verification. This makes it possible for authenticated attackers, with Subscriber-level access and above, to overwrite the site's Office 365 OAuth mail configuration (access token, refresh token, and user email) via a crafted URL. The configuration option is used during wizard setup of Microsoft365 SMTP, only available in the Pro option of the plugin. This could cause an Administrator to believe an attacker-controlled Azure app is their own, and lead them to connect the plugin to the attacker's account during configuration after upgrading to Pro.

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 <= 3.6.1.

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 'handle_gmail_oauth_redirect' function. This makes it possible for authenticated attackers, with subscriber level access and above, to inject invalid or attacker-controlled OAuth credentials. CVE-2025-67563 appears to be a duplicate of this issue.

The Post SMTP – Complete SMTP Solution with Logs, Alerts, Backup SMTP & Mobile App plugin for WordPress is vulnerable to unauthorized access of data due to a missing capability check on the __construct function in all versions up to, and including, 3.6.0. This makes it possible for unauthenticated attackers to read arbitrary logged emails sent through the Post SMTP plugin, including password reset emails containing password reset links, which can lead to account takeover.

The Post SMTP – WP SMTP Plugin with Email Logs and Mobile App for Failure Notifications – Gmail SMTP, Office 365, Brevo, Mailgun, Amazon SES and more plugin for WordPress is vulnerable to unauthorized modification of data due to a missing capability check on the 'update_post_smtp_pro_option_callback' function in all versions up to, and including, 3.4.1. This makes it possible for authenticated attackers, with Subscriber-level access and above, to enable pro extensions.

Authentication Bypass Using an Alternate Path or Channel vulnerability in Saad Iqbal Post SMTP post-smtp allows Authentication Bypass.This issue affects Post SMTP: from n/a through <= 3.2.0.

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.

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.

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.

Improper Neutralization of Special Elements used in an SQL Command ('SQL Injection') vulnerability in Saad Iqbal Post SMTP post-smtp allows Blind SQL Injection.This issue affects Post SMTP: from n/a through <= 2.9.9.

Missing Authorization vulnerability in Post SMTP Post SMTP Mailer/Email Log.This issue affects Post SMTP Mailer/Email Log: from n/a through 2.8.6.

The POST SMTP – The #1 WordPress SMTP Plugin with Advanced Email Logging and Delivery Failure Notifications plugin for WordPress is vulnerable to time-based SQL Injection via the selected parameter in all versions up to, and including, 2.9.3 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 access or higher to append additional SQL queries into already existing queries that can be used to extract sensitive information from the database.

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 Mailer – Email log, Delivery Failure Notifications and Best Mail SMTP for WordPress plugin for WordPress is vulnerable to unauthorized access of data and modification of data due to a type juggling issue on the connect-app REST endpoint in all versions up to, and including, 2.8.7. This makes it possible for unauthenticated attackers to reset the API key used to authenticate to the mailer and view logs, including password reset emails, allowing site takeover. CVE-2023-52233 appears to be a duplicate of this issue.

The POST SMTP WordPress plugin before 2.8.7 does not sanitise and escape the msg parameter before outputting it back in the page, leading to a Reflected Cross-Site Scripting which could be used against high privilege users such as admin.

The POST SMTP Mailer – Email log, Delivery Failure Notifications and Best Mail SMTP for WordPress plugin for WordPress is vulnerable to Reflected Cross-Site Scripting via the ‘msg’ parameter in all versions up to, and including, 2.8.6 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that execute if they can successfully trick a user into performing an action such as clicking on a link. CVE-2023-6621 appears to be a duplicate of this issue. CVE-2024-29128 appears to be a duplicate of this issue.

The POST SMTP Mailer – Email log, Delivery Failure Notifications and Best Mail SMTP for WordPress plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the ‘device’ header in all versions up to, and including, 2.8.7 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 Mailer plugin for WordPress is vulnerable to Cross-Site Request Forgery in versions up to, and including, 2.0.20. This is due to missing or incorrect nonce validation on the handleCsvExport() function. This makes it possible for unauthenticated attackers to trigger a CSV export via a forged request granted they can trick a site administrator into performing an action such as clicking on a link.

The Post SMTP plugin for WordPress is vulnerable to Stored Cross-Site Scripting via email contents in versions up to, and including, 2.5.7 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.