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CVE-2026-15421

MEDIUMCVSS 6.4/10EPSS 0.30%

Last modified

CVE-2026-15421 is a medium-severity vulnerability rated 6.4/10 on the CVSS scale. 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. EPSS estimates a 0.30% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1
6.4/10

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N

EPSS Probability
0.30%

22.6th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

VendorProductVersions
sitegroundSpeed Optimizer – The All-In-One Performance-Boosting Plugin<= 7.8.0

References

Timeline

Published
Last Modified
Status
Deferred

Frequently Asked Questions

What is CVE-2026-15421?
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.
How severe is CVE-2026-15421?
CVE-2026-15421 has a CVSS score of 6.4/10 (MEDIUM severity). The EPSS model estimates a 0.30% probability of exploitation in the next 30 days.
How do I fix CVE-2026-15421?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST