CVE-2026-15421

Deferred Deferred - Pending Action

Stored XSS in Speed Optimizer WordPress Plugin

Publication date: 2026-08-19

Last updated on: 2026-08-20

Assigner: Wordfence

Description

The Speed Optimizer – The All-In-One Performance-Boosting Plugin plugin for WordPress is vulnerable to Stored Cross-Site Scripting via Image Tag Attributes in all versions up to, and including, 7.8.0 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. This is only exploitable when the site administrator has enabled the Lazy Load Media option in the plugin settings.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-08-19

Last Modified

2026-08-20

Generated

2026-09-08

AI Q&A

2026-08-19

EPSS Evaluated

2026-09-07

NVD

CVE-2026-15421

EUVD

EUVD-2026-62219

Affected Vendors & Products

Vendor	Product	Version / Range
wp_speed_optimizer	speed_optimizer	to 7.8.0 (inc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-79	The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.

Attack-Flow Graph

Executive Summary

This vulnerability is a Stored Cross-Site Scripting (XSS) issue in the Speed Optimizer WordPress plugin. It allows authenticated attackers with contributor-level access or higher to inject malicious scripts into web pages by exploiting insufficient input sanitization and output escaping. The attack is possible only if the site administrator has enabled the Lazy Load Media option in the plugin settings.

Detection Guidance

Detection involves checking for the vulnerable plugin version and scanning for malicious scripts injected via Image Tag Attributes. Use WordPress admin to verify plugin version under Plugins. Check site files for unusual scripts in pages using Lazy Load Media. No specific commands are provided in the context.

Impact Analysis

If exploited, this vulnerability could allow attackers to execute arbitrary web scripts on your site whenever a user visits an affected page. This could lead to unauthorized actions, data theft, or defacement of your website. Attackers need contributor-level access or higher to exploit it.

Compliance Impact

This vulnerability could lead to data breaches or unauthorized access, which may violate GDPR, HIPAA, or other privacy regulations. If user data is compromised due to this exploit, organizations could face legal penalties, fines, or reputational damage.

Mitigation Strategies

Immediately update the Speed Optimizer plugin to the latest version beyond 7.8.0. Disable the Lazy Load Media option in plugin settings if enabled. Remove any unauthorized scripts from pages. Monitor for suspicious activity.

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