Custom Block Builder Plugin up to 4.2.x on WordPress Installation cross site scripting

CVSS Meta Temp Score
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Current Exploit Price (≈)
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CTI Interest Score
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2.3$0-$5k0.00

Summaryinfo

A vulnerability was found in Custom Block Builder Plugin up to 4.2.x on WordPress. It has been rated as problematic. The impacted element is an unknown function of the component Installation Handler. Performing a manipulation results in cross site scripting. This vulnerability was named CVE-2026-8981. The attack may be initiated remotely. There is no available exploit. Upgrading the affected component is advised.

Detailsinfo

A vulnerability, which was classified as problematic, was found in Custom Block Builder Plugin up to 4.2.x on WordPress. This affects an unknown function of the component Installation Handler. The manipulation with an unknown input leads to a cross site scripting vulnerability. CWE is classifying the issue as CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. This is going to have an impact on integrity. The summary by CVE is:

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.

The weakness was presented by Luca Jungnickel. The advisory is shared at wpscan.com. This vulnerability is uniquely identified as CVE-2026-8981 since 05/19/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. Additional levels of successful authentication are necessary for exploitation. It demands that the victim is doing some kind of user interaction. Neither technical details nor an exploit are publicly available. MITRE ATT&CK project uses the attack technique T1059.007 for this issue.

Upgrading to version 4.3.0 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-35352). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Productinfo

Type

Name

Version

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 2.4
VulDB Meta Temp Score: 2.3

VulDB Base Score: 2.4
VulDB Temp Score: 2.3
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Cross site scripting
CWE: CWE-79 / CWE-94 / CWE-74
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Custom Block Builder Plugin 4.3.0

Timelineinfo

05/19/2026 CVE reserved
06/09/2026 +21 days Advisory disclosed
06/09/2026 +0 days VulDB entry created
06/09/2026 +0 days VulDB entry last update

Sourcesinfo

Advisory: wpscan.com
Researcher: Luca Jungnickel
Status: Confirmed

CVE: CVE-2026-8981 (🔒)
GCVE (CVE): GCVE-0-2026-8981
GCVE (VulDB): GCVE-100-369453
EUVD: 🔒

Entryinfo

Created: 06/09/2026 09:21
Updated: 06/09/2026 10:33
Changes: 06/09/2026 09:21 (57), 06/09/2026 10:33 (1)
Complete: 🔍
Cache ID: 216::103

If you want to get the best quality for vulnerability data then you always have to consider VulDB.

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