CVE-2025-53523VulnerabilityPublished 12 Dec 2025

CVE-2025-53523: Japan Total System GroupSession Free edition · Cross-site scripting (XSS)

Affects Japan Total System GroupSession Free editionSource CVE Database V5

Not known to be exploited · CVSS 5.4 Medium : upgrade to 5.3.0 when convenient.

Data as of 25 Oct 2026, 19:02 UTC

CVSS 3.0 base score

5.4Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.1% chance of exploitation in 30 days – higher than 6% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 5.3.0

CVSS:3.0/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

Attack Vector: Network
Attack Complexity: Low
Privileges Required: Low
User Interaction: Required
Scope: Changed
Confidentiality: Low
Integrity: Low
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: Required: Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited.
Scope: Changed: An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.
Confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 12 Dec 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-25.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade Japan Total System GroupSession Free edition to 5.3.0.

Affected software

Product	Affected	Fixed in
Japan Total System Co.,Ltd. GroupSession Free edition	Affected <5.3.0	Fixed in 5.3.0

AI-suggested

European organizations using GroupSession products should immediately verify their software versions and upgrade to the fixed releases: Free edition version 5.3.0 or later, byCloud version 5.3.3 or later, and ZION version 5.3.2 or later. If immediate upgrades are not feasible, implement strict input validation and output encoding on all user-generated content within the application to prevent script injection. Employ Content Security Policy (CSP) headers to restrict script execution sources and reduce the impact of any injected scripts. Conduct user awareness training emphasizing the risks of clicking on suspicious links or pages within the collaboration platform. Monitor logs for unusual user activity or attempts to inject scripts. Limit user privileges to the minimum necessary to reduce the number of users capable of injecting malicious content. Engage with the vendor for official patches and security advisories. Regularly review and update web application firewall (WAF) rules to detect and block XSS payloads targeting GroupSession URLs. Finally, implement multi-factor authentication (MFA) to reduce the risk of compromised credentials being used to exploit this vulnerability.

Description

Stored cross-site scripting vulnerabilities exist in GroupSession Free edition prior to ver5.3.0, GroupSession byCloud prior to ver5.3.3, and GroupSession ZION prior to ver5.3.2. 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.

Impact

For European organizations, this vulnerability poses a moderate risk primarily to confidentiality and integrity of data within GroupSession environments. Attackers with valid user credentials can embed malicious scripts that execute in other users' browsers, potentially leading to session hijacking, unauthorized data access, or manipulation of displayed information. This can undermine trust in collaboration platforms and expose sensitive corporate or personal data. Although availability is not directly impacted, the indirect effects of data leakage or unauthorized actions could disrupt business operations or compliance with data protection regulations such as GDPR. Organizations in sectors relying heavily on collaborative tools for sensitive communications—such as finance, healthcare, and government—may face heightened risks. The requirement for authenticated access and user interaction limits the attack surface but does not eliminate the threat, especially in environments with many users or insufficient user training. The absence of known exploits reduces immediate risk but should not lead to complacency.

Summary

CVE-2025-53523 is a stored cross-site scripting (XSS) vulnerability identified in Japan Total System Co., Ltd.'s GroupSession collaboration software, specifically affecting the Free edition prior to version 5.3.0, byCloud prior to 5.3.3, and ZION prior to 5.3.2. The vulnerability allows an authenticated user to inject malicious scripts into pages or URLs within the application. When other users access these crafted pages, the embedded scripts execute in their browsers under the context of the vulnerable web application. This can lead to unauthorized actions such as session hijacking, theft of sensitive information, or manipulation of the user interface, thereby compromising confidentiality and integrity. The attack vector is network-based, requiring the attacker to have valid credentials (low privilege) and some user interaction (victim must access the malicious content). The vulnerability does not impact availability. The CVSS 3.0 score of 5.4 reflects these factors: network attack vector (AV:N), low attack complexity (AC:L), privileges required (PR:L), user interaction required (UI:R), scope changed (S:C), and partial impacts on confidentiality (C:L) and integrity (I:L). No public exploits are currently known, but the vulnerability is published and should be addressed promptly. The lack of patch links suggests users should consult the vendor for updates or apply available version upgrades to 5.3.0 or later.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 19 Dec 2025, 08:32 UTC

Technical details

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