Blocksy Companion dynamic-data blocks permit Author-level stored cross-site scripting

Blocksy Companion through 2.1.51 insufficiently sanitizes and escapes the tagName attribute of the blocksy/dynamic-data block. An Author or higher can store script in page content that executes in the site's origin whenever another user views the affected page.

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

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

Component: Blocksy Companion
Plugin slug: blocksy-companion
Affected: <= 2.1.51
Safe version: See mitigation notes
Published: Sep 01, 2026
Weakness: CWE-79 — Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

This CVE was published Sep 01, 2026 and is one of 13 known issues for this plugin.

What to do

Update, patch or deactivate.

Update to a confirmed release newer than 2.1.51 when available. Until then, restrict untrusted Author access or disable the affected dynamic-data block when warranted, remove malicious block attributes, and invalidate privileged sessions if affected pages were viewed.

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 Blocksy Companion plugin for WordPress is vulnerable to Stored Cross-Site Scripting via 'tagName' Block Attribute (blocksy/dynamic-data) in all versions up to, and including, 2.1.51 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with author-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.

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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