CVE-2024-12878: The Custom Block Builder WordPress plugin before 3.8.3 does not sanitise and escape a parameter before output

Q: How do I fix CVE-2024-12878?

lazy blocks: upgrade to 3.8.3. Exact commands for each OS are on this page.

Q: Is CVE-2024-12878 being exploited?

CVE-2024-12878 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2024-12878 affect?

CVE-2024-12878 affects lazy blocks. Severity is high (CVSS 7.1). 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 adm

Q: How urgent is CVE-2024-12878?

Priority 42/100. High severity; Public exploit reference

This month

HIGH 7.1UPGRADE

CVE-2024-12878 is a high-severity flaw (CVSS 7.1) affecting lazy blocks. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

High severity
Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	7.1 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.6% (top 51%)
CISA exploited list	No
Weakness	CWE-79
Published	2025-02-26
Last modified	2026-06-17

Publisher (CNA): WPScan · Vendor: thedevoice

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2025-02-26 13:15 UTCPublished CVE record published
2026-06-17 07:00 UTCUpdated Record last modified

thedevoice lazy blocks UPGRADE

Affected: < 3.8.3

Fixed in: 3.8.3

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy lazy-blocks || rpm -q lazy-blocks || lazy-blocks --version

2. UPGRADE to 3.8.3 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade lazy-blocks

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade lazy-blocks

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Nuclei scan template: Lazy Blocks <= 3.8.2 - Cross-Site Scripting

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2024-12878?

lazy blocks: upgrade to 3.8.3. Exact commands for each OS are on this page.

Is CVE-2024-12878 being exploited?

CVE-2024-12878 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2024-12878 affect?

CVE-2024-12878 affects lazy blocks. Severity is high (CVSS 7.1). 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 adm

How urgent is CVE-2024-12878?

Priority 42/100. High severity; Public exploit reference

Software pages

WordPress vulnerabilities

References

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