The Blocksy theme for WordPress is vulnerable to PHP Object Injection leading to Remote Code Execution via the 'blocksy_meta' REST API field and the V200 database migration in versions up to and including 2.1.35. This is due to insufficient input sanitization in the blocksy_sanitize_post_meta_options() function, which only blocks values containing '<' or '>' and does not prevent serialized PHP object strings from being stored in post meta, combined with the SearchReplacer::run_recursively() function unconditionally deserializing all string values via @unserialize() during migration without restricting allowed classes. This makes it possible for authenticated attackers, with contributor-level access and above, to inject a serialized Blocksy\RaiiPattern object into post meta that, when the V200 migration runs on an upgraded site, is deserialized and triggers RaiiPattern::__destruct(), which executes arbitrary PHP callables via call_user_func().
CVE-2026-8365 is a high severity with CVSS 8.8 Remote Code Execution issue affecting the Theme Blocksy. It affects Versions up to 2.1.41 and is fixed in 2.1.42.
Use the related hub and response guides to connect this CVE-2026-8365 report with patch validation, scanner checks, and site hardening work.
Open the grouped hub for related CVEs, affected ranges, severity mix, and patch coverage.
Check access, XML-RPC exposure, backup readiness, and monitoring after patching.
Use containment, evidence capture, remediation, and validation steps when exploit risk is high.
CVE-2026-8365 is tracked for the Theme Blocksy as high severity with CVSS 8.8. The affected range is Versions up to 2.1.41. Update Blocksy to 2.1.42 or newer where that version is compatible with the site.
Search engines and operators need more than a title. This page exposes the identifier, affected range, patch evidence, and source coverage that make the vulnerability actionable.
This report has a CVE identifier, which makes it suitable for focused search and vulnerability triage workflows.
Affected version data gives operators a concrete comparison point against installed WordPress software.
A fixed version is present, so the page can answer update and remediation intent directly.
External references are available for source validation, advisory review, and incident notes.
Use these checks when converting this record into a patch ticket, incident note, or risk acceptance decision.
Inventory the installed Theme package and compare its version with Versions up to 2.1.41.
Confirm Blocksy is updated to 2.1.42 or newer.
Review references and CVSS vector details for exploitability, authentication requirements, and exposure path.
After patching, re-run vulnerability monitoring and keep the related plugin or theme hub under review for follow-up CVEs.
| Software Type | Theme |
|---|---|
| Software Slug |
blocksy
View on wordpress.org
|
| CVE | CVE-2026-8365 |
| Patched Versions |
2.1.42
|
| Affected Versions |
Versions up to 2.1.41
|
These internal links group the same WordPress theme by CVE, issue type, severity, and patch status so operators and search engines can connect the full vulnerability cluster.
Blocksy <= 2.1.30 - Authenticated (Contributor+) Stored Cross-Site Scripting via `blocksy_meta` Fields
Blocksy <= 2.0.77 - Authenticated (Contributor+) Stored Cross-Site Scripting
Blocksy <= 2.0.50 - Authenticated (Contributor+) Stored Cross-Site Scripting
Blocksy <= 2.0.46 - Authenticated (Contributor+) Stored Cross-Site Scripting
Blocksy <= 2.0.42 - Authenticated (Contributor+) Stored Cross-Site Scripting
Blocksy <= 2.0.39 - Authenticated (Contributor+) Stored Cross-Site Scripting via About Me block
Blocksy <= 2.0.33 - Authenticated (Contributor+) Stored Cross-Site Scripting
Blocksy <= 2.0.26 - Authenticated (Contributor+) Stored Cross-Site Scripting
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