---
id: CVE-2025-66284
title: >-
  Stored cross-site scripting vulnerabilities exist in GroupSession Free edition
  prior to ver5.7.1, GroupSession byCloud prior to ver5.7.1, and GroupSession
  ZION prior to ver5.7.1
summary: >-
  Stored cross-site scripting vulnerabilities exist in GroupSession Free edition
  prior to ver5.7.1, GroupSession byCloud prior to ver5.7.1, and GroupSession
  ZION prior to ver5.7.1. A logged-in user can prepare a malicious page or URL,
  and …
severity: medium
cvss: 5.4
cvssVector: 'CVSS:3.0/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N'
cwe:
  - CWE-79
vendor: groupsession
product: groupsession
affected:
  - groupsession < 5.7.1
patched:
  - groupsession 5.7.1
published: '2025-12-12'
updated: '2026-10-07'
sourceUpdated: '2026-10-07T20:10:01.970'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-66284'
references:
  - url: 'https://groupsession.jp/info/info-news/security20251208'
    label: vultures@jpcert.or.jp
  - url: 'https://jvn.jp/en/jp/JVN19940619/'
    label: vultures@jpcert.or.jp
tags:
  - nvd
epss: 0.00173
epssPercentile: 0.06097
ingestedAt: '2026-10-07T20:46:46.892Z'
---

## Overview

Stored cross-site scripting vulnerabilities exist in GroupSession Free edition prior to ver5.7.1, GroupSession byCloud prior to ver5.7.1, and GroupSession ZION prior to ver5.7.1. A logged-in user can prepare a malicious page or URL, and an arbitrary script may be executed on the web browser when another user accesses it.

## Affected

- `groupsession < 5.7.1`

## Remediation

Upgrade past the affected range:

- `groupsession 5.7.1`