CVE-2026-17011Public exploitNetwork attack vector

Contributor-level defacement via unrestricted global CSS write

Published Aug 9, 2026 · Updated Aug 9, 2026

Stored CSS injection in POSIMYTH Innovations Nexter Blocks before 5.0.2 allows remote authenticated users to deface site pages. The plus_save_block_css REST route accepts global_css from Contributors because its permission callback checks only edit_posts, then writes it verbatim to the public plus-global.css file. A Contributor account and REST nonce are required; injected rules load site-wide and can hide content, overlay pages, or redress the interface.

CVSS severity3.8
Low
EPSS probability0.12%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored CSS injection in POSIMYTH Innovations Nexter Blocks before 5.0.2 allows remote authenticated users to deface site pages. The plus_save_block_css REST route accepts global_css from Contributors because its permission callback checks only edit_posts, then writes it verbatim to the public plus-global.css file. A Contributor account and REST nonce are required; injected rules load site-wide and can hide content, overlay pages, or redress the interface.

The record

CVE
CVE-2026-17011
Published
Aug 9, 2026
Updated
Aug 9, 2026
Vendor
POSIMYTH Innovations
Product
Nexter Blocks
Classifications
CWE-345, T1491.002
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 9, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 9, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <5.0.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

POSIMYTH Innovations · Nexter Blocksversion=0 <5.0.2

Published CVSS scores

3.8CISA-ADPCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:L/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-345Insufficient Verification of Data Authenticity
T1491.002External Defacement

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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