FluentSMTP <= 2.0.0 - Authenticated (Admin+) Stored Cross-Site Scripting
Strategic Overview
- Status
- Patched in 2.0.1
- Affected Plugin
- FluentSMTP – WP Mail SMTP Plugin with Amazon SES, SendGrid, Mailgun, Postmark, Cloudflare, toSend, Gmail and Any SMTP
- Affected Version
< 2.0.1- CVSS
- 5.5Medium
- Weakness type
- CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
- CVE
CVE-2021-24528
At a glance
CVE-2021-24528 is a medium-severity Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in the FluentSMTP WordPress plugin, affecting versions < 2.0.1. It carries a CVSS score of 5.5 (reachable over the network; low attack complexity). Exploitation requires an authenticated account at Admin level or above. The issue is fixed in version 2.0.1; sites on affected versions should update now. Disclosed July 2021, reported by YoshiKen.
Vulnerability Overview
The FluentSMTP WordPress plugin before 2.0.1 does not sanitize parameters before storing the settings in the database, nor does the plugin escape the values before outputting them when viewing the SMTP settings set by this plugin, leading to a stored cross site scripting (XSS) vulnerability. Only users with roles capable of managing plugins can modify the plugin's settings.
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 interaction from a victim user.
CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Reaching this weakness in FluentSMTP < 2.0.1 takes an account at Admin level or above. 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 2.0.1: builds < 2.0.1 are affected, anything from 2.0.1 onward is not.
Remediation
Update to version 2.0.1, or a newer patched version
How does WordSec protect against this?
An attacker needs Admin access first, so the firewall sees the attempt as traffic from a logged-in account: WordSec's web application firewall inspects request payloads before WordPress loads them. None of that substitutes for the fix: FluentSMTP 2.0.1 closes this, and updating the plugin is the step that ends it.
- Firewall
- Alerts
External References
Related records
Same weakness class
Other vulnerabilities in FluentSMTP – WP Mail SMTP Plugin with Amazon SES, SendGrid, Mailgun, Postmark, Cloudflare, toSend, Gmail and Any SMTP
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