CVE-2026-15421: Speed Optimizer <= 7.8.0 - Authenticated (Contributor+) Stored Cross-Site Scripting via Image Tag Attributes
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.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Configuration
Disable the plugin setting “Lazy Load Media” because the stored XSS is only exploitable when this option is enabled.
Speed Optimizer – The All-In-One Performance-Boosting Plugin (WordPress) Lazy Load Media option = disabled
Event History
Frequently Asked Questions
Which sites are exposed to this issue?
Sites using Speed Optimizer versions up to and including 7.8.0 are exposed only if the plugin's Lazy Load Media option is enabled. The issue affects WordPress installations where users have contributor-level or higher access.
What access does an attacker need to exploit it?
An attacker must be authenticated to the WordPress site and have at least contributor-level permissions. No victim interaction is required for injection, but the stored script executes when someone accesses the affected page.
Does disabling Lazy Load Media mitigate the issue?
Yes. Exploitation is only possible when the Lazy Load Media option is enabled in the plugin settings, so disabling that option prevents this documented attack path if patching cannot be performed immediately.