CVE-2025-54856: Cross-site Scripting (XSS) in Six Apart Ltd. Movable Type (Cloud Edition)

5

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 0.2% (30-day exploitation probability)+2
Technical severity (medium)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

0.23%

ahead of 13% of scored CVEs · Oct 14, 2026

Affects

Six Apart Ltd.

Movable Type (Cloud Edition) and 5 more

CVSS base

4.8

Medium · 2 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation

None

none · proof-of-concept · active

Automatable

No

can an attacker script the kill-chain steps

Technical impact

Partial

partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Six Apart Ltd. Movable Type (Cloud Edition), Six Apart Ltd. Movable Type (Software Edition), Six Apart Ltd. Movable Type Advanced (Software Edition)…).
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Exploitation requires user interaction: tighten email/web filtering and warn affected users.
Search available logs for exploit probes matching the vulnerability class (cross-site scripting), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Six Apart Ltd.	Movable Type (Cloud Edition)	version 8.7.0 (8 series)version 7 r.5509 (7 series)	Vulnerable	CVE Program (cve.org) e CISA ADP
Six Apart Ltd.	Movable Type (Software Edition)	version 8.4.0 to 8.4.3 (8.4 series)version 8.0.0 to 8.0.7 (8.0 series)version 7 r.5509 and earlier (7 series)	Vulnerable	CVE Program (cve.org) e CISA ADP
Six Apart Ltd.	Movable Type Advanced (Software Edition)	version 8.4.0 to 8.4.3 (8.4 series)version 8.0.0 to 8.0.7 (8.0 series)version 7 r.5509 and earlier (7 series)	Vulnerable	CVE Program (cve.org) e CISA ADP
Six Apart Ltd.	Movable Type Premium (Advanced Edition) (Software Edition)	version 2.10 and earlier (2 series)version 1.67 and earlier (1 series)	Vulnerable	CVE Program (cve.org) e CISA ADP
Six Apart Ltd.	Movable Type Premium (Cloud Edition)	version 2.10 (2 series)version 1.67 (1 series)	Vulnerable	CVE Program (cve.org) e CISA ADP
Six Apart Ltd.	Movable Type Premium (Software Edition)	version 2.10 and earlier (2 series)version 1.67 and earlier (1 series)	Vulnerable	CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Network

Attack complexity

Low

Privileges required

High

User interaction

Required

Scope

Changed

Confidentiality

Low

Integrity

Low

Availability

None

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
4.6	CVSS 4.0	Medium	—	—	vultures@jpcert.or.jp via NIST National Vulnerability Database
4.6	CVSS 4.0	Medium	—	—	jpcert via CVE Program (cve.org) e CISA ADP
4.8	CVSS 3.0	Medium	1.7	2.7	vultures@jpcert.or.jp via NIST National Vulnerability Database
4.8	CVSS 3.0	Medium	—	—	jpcert via CVE Program (cve.org) e CISA ADP

CVSS:3.0/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N (score shown at the top: vultures@jpcert.or.jp)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-79 · Cross-site Scripting (XSS)

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 0.23%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
Monitor CSP violation reports and script payloads in reflected parameters.

web/proxy/WAF logsnetwork IDS/IPSapplication logs

Timeline

What happened to this CVE, newest first.

2026
Affected products added · six apart ltd./movable type (software edition), six apart ltd./movable type advanced (software edition), six apart ltd./
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
SSVC assessment updated
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 13, 2026
CVSS changed · 4.8
Oct 13, 2026 · NIST National Vulnerability Database
Source status changed · → Deferred
Oct 13, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 13, 2026 · NIST National Vulnerability Database
2025
CVE published
Oct 23, 2025 · jpcert

Source activity

Repeated readings are counted rather than listed.

1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

3 on the record

www.sixapart.jp/movabletype/news/2025/10/22-1055.html
NIST National Vulnerability Database
movabletype.org/news/2025/10/mt-880-released.html
NIST National Vulnerability Database
jvn.jp/en/jp/JVN24333679/
NIST National Vulnerability Database

Elsewhere on this site

Six Apart Ltd.
every CVE for this vendor

Cross-site scripting
same class

CWE-79
other pages naming this weakness

Related CVEs (same products)

Critical CVE-2026-96408 Code Injection in Six Apart Ltd. Movable Type (Cloud Edition) 8d
High CVE-2026-103668 SQL Injection in Six Apart Ltd. Movable Type (Cloud Edition) 8d
Medium CVE-2026-23704 Unrestricted Upload of File with Dangerous Type in Six Apart Ltd. Movable Type (Software Edition) Feb 4, 2026
Medium CVE-2026-21393 Cross-site Scripting (XSS) in Six Apart Ltd. Movable Type (Software Edition) Feb 4, 2026
Medium CVE-2026-22875 Cross-site Scripting (XSS) in Six Apart Ltd. Movable Type (Software Edition) Feb 4, 2026
Medium CVE-2026-24447 CSV Injection in Six Apart Ltd. Movable Type (Software Edition) Feb 4, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No fixed version, patch or mitigation documented.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2025-54856 is "Cross-site Scripting (XSS) in Six Apart Ltd. Movable Type (Cloud Edition)", rated Medium. It affects Movable Type (Cloud Edition) (Six Apart Ltd.); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 4.8 describes technical severity. EPSS 0.23% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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