CVE-2026-154216.4MediumCWE-79

CVE-2026-15421: Speed Optimizer <= 7.8.0 - Authenticated (Contributor+) Stored Cross-Site Scripting via Image Tag Attributes

siteground · Speed Optimizer – The All-In-One Performance-Boosting Plugin

Affected: siteground Speed Optimizer – The All-In-One Performance-Boosting Plugin · Exploitation: unlikely (under 1%)

Not in CyberSIXT coverage yet: no article names this CVE. This page shows the public record.

0.4%probability of exploitation in the next 30 days

35th percentile

050100

Higher than 35% of scored CVEs

6.4MediumCVSS 3.1

LowMediumHighCrit.

DescriptionCVE.org

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 products1

From the CVE record. A product or version that is not listed is unknown, not unaffected.

siteground · Speed Optimizer – The All-In-One Performance-Boosting Pluginup to and including 7.8.0

On the Atlas

Every published CVE is on the CyberSIXT Atlas, grouped by weakness, vendor and month.

Open the Atlas

Exploitation: Unlikely (under 1%). EPSS under 1%, or no score yet.
CISA KEV: Not listed
Public check: No public nuclei template
Weakness: Cross-site Scripting
Vendor: siteground
Published: August 2026
Band: Unlikely (under 1%), August 2026

CoverageNo articles yet

No CyberSIXT article names CVE-2026-15421 yet, so there is no coverage timeline, action brief or change log for it. Everything on this page comes from the public CVE record, CISA KEV, EPSS and the nuclei template index. Search the archive or see the CVEs in the news.