FluentSMTP <= 2.2.95 - Unauthenticated Stored Cross-Site Scripting via Recipient Display Name (to.name) in Email Logs
Strategic Overview
- Status
- Patched in 2.3.0
- Affected Plugin
- FluentSMTP – WP SMTP Plugin with Amazon SES, SendGrid, Mailgun, Postmark, Cloudflare, toSend, Gmail and Any SMTP
- Affected Version
<= 2.2.95- CVSS
- 7.2High
- Weakness type
- CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
- CVE
CVE-2026-16636
At a glance
CVE-2026-16636 is a high-severity Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in the FluentSMTP WordPress plugin, affecting versions <= 2.2.95. It carries a CVSS score of 7.2 (reachable over the network; low attack complexity). Exploitation requires no authentication. The issue is fixed in version 2.3.0; sites on affected versions should update now. Disclosed August 2026, reported by Fraudless.
Vulnerability Overview
The FluentSMTP – WP SMTP Plugin with Amazon SES, SendGrid, MailGun, Postmark, Google and Any SMTP Provider plugin for WordPress is vulnerable to Stored Cross-Site Scripting via Recipient Display Name (to.name) in Email Logs in all versions up to, and including, 2.2.95 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 payload is delivered via an attacker-controlled recipient display name (to.name) in a wp_mail() call and does not fire in the log list view — only in the detail view when an administrator uses the Prev/Next navigation controls, as that path bypasses the escapeHtml pipeline used by the list view.
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.
CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
FluentSMTP <= 2.2.95 carries this weakness at wp_mail(), and reaching it takes no account at all. Cross-site scripting happens when input from a request is written into a page without being escaped for the context it lands in, so the browser parses attacker-supplied text as markup or script.
Injected script runs with the privileges of whoever views the affected page, which is how these flaws turn into administrator session theft, silent account creation or persistent backdoors in page content. For FluentSMTP the fix is 2.3.0: builds <= 2.2.95 are affected, anything from 2.3.0 onward is not.
Remediation
Update to version 2.3.0, or a newer patched version
How WordSec helps
Requests carrying this pattern arrive without a session, so nothing upstream of the firewall gets a chance to reject them: WordSec's web application firewall inspects request payloads before WordPress loads them. None of that substitutes for the fix: FluentSMTP 2.3.0 closes this, and updating the plugin is the step that ends it.
- Firewall
- Login Security
- Alerts
External References
Related records
Same weakness class
Other vulnerabilities in FluentSMTP – WP SMTP Plugin with Amazon SES, SendGrid, Mailgun, Postmark, Cloudflare, toSend, Gmail and Any SMTP
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