POST SMTP Mailer – Email log, Delivery Failure Notifications and Best Mail SMTP for WordPress <= 2.8.7 - Authorization Bypass via type connect-app API
Strategic Overview
- Status
- Patched in 2.8.8
- Affected Plugin
- Post SMTP – Complete Email Deliverability and SMTP Solution with Email Logs, Alerts, Backup SMTP & Mobile App
- Affected Version
<= 2.8.7- CVSS
- 9.8Critical
- Weakness type
- CWE-639 · Authorization Bypass Through User-Controlled Key
- CVE
CVE-2023-6875
At a glance
CVE-2023-6875 is a critical-severity Authorization Bypass Through User-Controlled Key vulnerability in the Post SMTP WordPress plugin, affecting versions <= 2.8.7. It carries a CVSS score of 9.8 (reachable over the network; low attack complexity; high confidentiality, integrity, availability impact). Exploitation requires no authentication. The issue is fixed in version 2.8.8; sites on affected versions should update now. Disclosed January 2024, reported by Ulyses Saicha.
Vulnerability Overview
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.
Technical Analysis
The vector marks this flaw as remotely reachable over the network, with low attack complexity — no special timing or configuration is needed, and no privileges on the target site, and no interaction from a victim user. A successful exploit has high impact on confidentiality, integrity, availability — full site compromise territory.
CWE-639: Authorization Bypass Through User-Controlled Key
Reaching this weakness in Post SMTP <= 2.8.7 takes a caller who can reach the endpoint. Authorization bypass through a user-controlled key, often called insecure direct object reference, means the application looks up a record by an identifier from the request without checking that the caller owns it.
Changing a number in the request is enough to read or modify other users' records, which on commerce and membership sites means customer data. For Post SMTP the fix is 2.8.8: builds <= 2.8.7 are affected, anything from 2.8.8 onward is not.
Remediation
Update to version 2.8.8, or a newer patched version
How does WordSec protect against this?
Because it turns on account access, WordSec's login security is the relevant layer: role-based two-factor, captcha and brute-force limits raise the cost of getting the account this needs. None of that substitutes for the fix: Post SMTP 2.8.8 closes this, and updating the plugin is the step that ends it.
- Login Security
- Alerts
External References
Related records
Other vulnerabilities in Post SMTP – Complete Email Deliverability and SMTP Solution with Email Logs, Alerts, Backup SMTP & Mobile App
- 9.8CVE-2025-11833: Post SMTP Account Takeover
CVE-2025-11833 - 8.8CVE-2025-24000: Post SMTP Authenticated (Subscriber+) Account Takeover
CVE-2025-24000 - 7.2CVE-2026-48838: Post SMTP Stored XSS
CVE-2026-48838 - 7.2CVE-2026-3090: Post SMTP <= 3.8.0 Stored Cross-Site Scripting
CVE-2026-3090 - 7.2CVE-2025-0521: Post SMTP <= 3.0.2 Stored Cross-Site Scripting
CVE-2025-0521 - 7.2CVE-2024-5207: POST SMTP Mailer SQL Injection
CVE-2024-5207 - 7.2CVE-2023-7027: POST SMTP Mailer Stored XSS
CVE-2023-7027 - 7.2CVE-2023-6620: POST SMTP Mailer SQL Injection
CVE-2023-6620
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