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CVE-2025-66284

20
FAUCET Score

CVE-2025-66284 describes stored cross-site scripting (XSS) vulnerabilities affecting GroupSession Free, byCloud, and ZION editions prior to version 5.7.1. A logged-in attacker can craft a malicious page or URL, leading to arbitrary script execution in another user's web browser upon access. The vulnerability has a CVSS score of 5.4 (Medium), indicating a network-based attack with low privileges and user interaction, potentially impacting confidentiality and integrity. Currently, there is no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
< 5.7.1CPE matchmatch criteria
cpe:2.3:a:groupsession:groupsession:*:*:*:*:bycloud:*:*:*
< 5.7.1CPE matchmatch criteria
cpe:2.3:a:groupsession:groupsession:*:*:*:*:free:*:*:*
< 5.7.1CPE matchmatch criteria
cpe:2.3:a:groupsession:groupsession:*:*:*:*:zion:*:*:*

CVSS Data

CVSS version used by this source: 4.0

4.8MEDIUM

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
LOW
User Interaction
ACTIVE
VS Confidentiality
NONE
VS Integrity
NONE
VS Availability
NONE
SS Confidentiality
LOW
SS Integrity
LOW
SS Availability
NONE
Exploit Maturity
NOT_DEFINED
CvssVersion
4.0

Exploit Intelligence

EPSS Score
0.15%
Probability of exploitation in next 30 days
EPSS Percentile
4.4%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0015 is in the 2nd percentile among its peer group of 15,225 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.0 Bluesky, 0.0 Mastodon, and 0.1 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.0 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

groupsession.jp / info/info-news/security20251208
Vendor Advisory
jvn.jp / en/jp/JVN19940619
Third Party Advisory