HomeWordPress vulnerabilitiesCustom Block Builder
Custom Block Builder vulnerabilities
Custom Block Builder has 3 known vulnerabilities in this database. The most recent published record is dated 9 Jun 2026.
- Known vulnerabilities
- 3
- Active installs
- 20,000+
- Latest version
- 4.4.1
- Last updated
- 31 Aug 2026
- Most recent
- 9 Jun 2026
Find it in your WordPress dashboard under Plugins. Severity is based on the CVSS score published with the CVE where one is available.
| Vulnerability | Severity | Affected | Fix | Published |
|---|---|---|---|---|
| Cross-site scripting (XSS) CVE-2026-8981 | Low 3.5 | Before 4.3.0 | Fixed in 4.3.0 | 9 Jun 2026 |
| Remote code execution CVE-2026-1560 | High 8.8 | Up to 4.2.0 | Fixed in a later version (latest 4.4.1) | 11 Feb 2026 |
| Cross-site scripting (XSS) CVE-2024-12878 | High 7.1 | Before 3.8.3 | Fixed in 3.8.3 | 26 Feb 2025 |
Read the published descriptions
- CVE-2026-8981, 9 Jun 2026
- The Custom Block Builder WordPress plugin before 4.3.0 does not consistently check the unfiltered_html capability across all paths that write to its block template code fields, allowing administrators on multisite installations (or single-site installs with DISALLOW_UNFILTERED_HTML defined) to inject arbitrary JavaScript that executes for any visitor of pages embedding the affected block. CVE record
- CVE-2026-1560, 11 Feb 2026
- The Custom Block Builder - Lazy Blocks plugin for WordPress is vulnerable to Remote Code Execution in all versions up to, and including, 4.2.0 via multiple functions in the 'LazyBlocks_Blocks' class. This makes it possible for authenticated attackers, with Contributor-level access and above, to execute code on the server. CVE record
- CVE-2024-12878, 26 Feb 2025
- The Custom Block Builder WordPress plugin before 3.8.3 does not sanitise and escape a parameter before outputting it back in the page, leading to a Reflected Cross-Site Scripting which could be used against high privilege users such as admin. CVE record
What to do if you run Custom Block Builder
If you run Custom Block Builder, open WordPress and check the installed version in Plugins. Compare it with the affected versions in the vulnerability record. If a fixed version is available, take a current backup and update to that version or the latest supported release.
If no fixed version exists, consider disabling and removing the plugin or replacing it with a maintained alternative. After dealing with the affected software, check administrator users, unexpected file changes, redirects, unfamiliar pages and security logs for signs that the site may already have been altered.
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