CVE-2026-23887Public exploitNetwork attack vector

Stored XSS via unencoded file metadata

Published Jan 21, 2026 · Updated Jan 21, 2026

Stored XSS in GroupOffice 6.8.148 and earlier and 25.0.1 through 25.0.79 allows remote authenticated users to run script via filenames. FileController.php returns the stored path and file extension to the file viewer without HTML encoding, so markup in an uploaded filename is interpreted by the browser. Exploitation requires file-upload access and another user to open the crafted file, exposing that user's session to browser actions within the file-viewing context.

CVSS severity5.1
Medium
EPSS probability0.26%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored XSS in GroupOffice 6.8.148 and earlier and 25.0.1 through 25.0.79 allows remote authenticated users to run script via filenames. FileController.php returns the stored path and file extension to the file viewer without HTML encoding, so markup in an uploaded filename is interpreted by the browser. Exploitation requires file-upload access and another user to open the crafted file, exposing that user's session to browser actions within the file-viewing context.

The record

CVE
CVE-2026-23887
Published
Jan 21, 2026
Updated
Jan 21, 2026
Vendor
Intermesh BV
Product
GroupOffice
Classifications
CWE-20, CWE-79, T1203
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 21, 2026CVE publishedPublication date reported by the CVE source.
  2. Jan 21, 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=>= 25.0.1, < 25.0.80
  2. Affected versionversion=< 6.8.149

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Intermesh BV · GroupOfficeversion=>= 25.0.1, < 25.0.80; version=< 6.8.149

Published CVSS scores

5.1GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
5.4NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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-20Improper Input Validation
CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1203Exploitation for Client Execution

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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