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Post SMTP <= 4.0.1 — Unauthenticated Stored DOM-Based Cross-Site Scripting via 'user_email' Parameter (Multisite Registration → Failed Email Log)

CVE-2026-75962Published · Updated

Action summary

Affected: ≤4.0.1Update to 4.0.2 or newer

All remediation steps
Watch plugin
Severity
High7.2
CVSS
7.2
CVSS 3.1 · CNA (Wordfence)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N
What does this vector mean?
AV:N Attack vector
Network
AC:L Attack complexity
Low
PR:N Privileges required
None
UI:N User interaction
None
S:C Scope
Changed
C:L Confidentiality
Low
I:L Integrity
Low
A:N Availability
None
Weakness
CWE-79 Cross-Site Scripting
Required access
No account needed
Exploit prediction (EPSS)
No score
CISA KEV
Not listed
On this page8

Am I affected?

Post SMTP – Complete Email Delivery and SMTP Solution with Email Logs, Alerts, Backup SMTP & Mobile App post-smtp

  1. Affected≤ 4.0.1
  2. Patched in4.0.2

Update to 4.0.2 or newer.

You are affected if you run ≤ 4.0.1. Version 4.0.2 and later are not affected by this issue.

  • Check your version: in wp-admin go to Plugins → Installed Plugins and read the version under Post SMTP – Complete Email Delivery and SMTP Solution with Email Logs, Alerts, Backup SMTP & Mobile App.
  • No admin access? Run a passive check of your site. It reads public files only.
  • No account is needed to exploit this. Treat any exposed site on an affected version as at risk.

What to do

  1. Update to version 4.0.2, or a newer patched version
  2. Rotate administrator passwords and application secrets if the site ran a vulnerable version while publicly reachable.
  3. Watch Post SMTP – Complete Email Delivery and SMTP Solution with Email Logs, Alerts, Backup SMTP & Mobile App to get an email when the next vulnerability is published.

Advisory

Source description from Wordfence Intelligence, credited to Adrien Brunner.

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.

Exploits & references

Proof-of-concept & detection

No public proof-of-concept or detection template is known for this vulnerability.

Advisories & patches

More in Post SMTP – Complete Email Delivery and SMTP Solution with Email Logs, Alerts, Backup SMTP & Mobile App

All 28
More vulnerabilities in Post SMTP – Complete Email Delivery and SMTP Solution with Email Logs, Alerts, Backup SMTP & Mobile App
SeverityVulnerabilityCVEPublished
Medium6.3Missing Authorization to Authenticated (Subscriber+) Settings Change
4.0.0-beta.1 – 4.0.0-beta.1Update to 4.0.1
CVE-2026-81278
High7.2Unauthenticated Stored Cross-Site Scripting
≤3.6.2Update to 3.6.3
CVE-2026-48838
Medium6.1Reflected DOM-Based Cross-Site Scripting via url Parameter
≤5.5.8Update to 5.5.9
CVE-2024-13362
High7.2Unauthenticated Stored Cross-Site Scripting via 'event_type'
≤3.8.0Update to 3.9.0
CVE-2026-3090
Medium5.3Missing Authorization to Authenticated (Subscriber+) Office 365 OAuth Configuration Overwrite
≤3.8.0Update to 3.9.0
CVE-2026-2559

Same weakness (Cross-Site Scripting)

All Cross-Site Scripting
Other Cross-Site Scripting vulnerabilities
SeverityVulnerabilityCVEPublished
High7.2Unauthenticated Stored Cross-Site Scripting via Comment User-Agent Header
EZ SQL Reports Shortcode Widget and DB Backup≤5.25.25Update to 5.26.45
CVE-2026-120688
Critical9.8Unauthenticated Arbitrary File Upload via File Upload via Public Form Submission
Chatterbug Forms – Fast, Flexible WordPress Form Builder≤1.0.2Update to 1.1
CVE-2026-125055
Critical9.8Unauthenticated PHP Object Injection to Remote Code Execution via 'form' Parameter
ELEX WordPress HelpDesk & Customer Ticketing System≤3.3.9Update to 3.4.0
CVE-2026-119077
Medium5.3Unauthenticated Sensitive Information Exposure in 'search' Parameter
Customer Reviews for WooCommerce≤5.127.0Update to 5.128.0
CVE-2026-121518

Timeline

  1. CVE published

    Severity high, CVSS 7.2

  2. Record last updated

Sources & licenses

Wordfence record
Vulnerability data
Wordfence Intelligence. [object Object] Licensed under the CC BY-SA 4.0.
CVE® identifiers
[object Object]. Used under the CVE Program. CVE® is a registered trademark of The MITRE Corporation.
CVSS / CWE
National Vulnerability Database (NVD), shown unmodified. This product uses the NVD API but is not endorsed or certified by the NVD.
VulnCrest content
Summary, remediation guidance and page layout © VulnCrest. Not sourced from NVD.

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