Speed Optimizer lazy-load image attributes permit Contributor stored XSS

Speed Optimizer through 7.8.0 insufficiently sanitizes and escapes image tag attributes when the administrator has enabled Lazy Load Media. A Contributor can place script-capable content in those attributes; the payload is stored in a page and executes whenever a visitor opens the injected page.

CVE / CNA score 6.4 CVSS 3.1 · security@wordfence.com

NVD score Pending NVD has not published its own CVSS assessment.

Component: Speed Optimizer – The All-In-One Performance-Boosting Plugin
Plugin slug: sg-cachepress
Affected: <= 7.8.0
Safe version: See mitigation notes
Published: Aug 19, 2026
Weakness: CWE-79 — Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

This CVE was published Aug 19, 2026 and is one of 2 known issues for this plugin.

What to do

Update, patch or deactivate.

No fixed release is identified in the authoritative record. Disable Lazy Load Media, restrict Contributor access and update when a release newer than 7.8.0 is confirmed to fix CVE-2026-15421. Review Contributor-authored image content for unexpected attributes.

No confirmed safe version is listed. Consider a vendor-supported patch or temporarily restricting the affected functionality while you assess the risk.

Deactivate only when warranted by your risk profile, or when advised by your hosting provider in the limited circumstances where the vulnerability cannot otherwise be mitigated. If you’re unsure which action is appropriate, contact Fused or your hosting provider for guidance.

Source record

Technical 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.

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

References

Primary and upstream sources

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