CVE Intelligence
Medium Cross-site scripting

CVE-2026-112958 — ApostropheCMS: Stored XSS via Unescaped Widget Style Attribute Serialization

ApostropheCMS is an open-source Node.js content management system. Prior to 4.34.0, a project-defined free-form widget style field can carry an editor-controlled quote into an inline style attribute because the wrapper serializer does not apply HTML-attribute encoding. The quote can terminate the style attribute and inject executable attributes when published content, or an affected draft viewed by a higher-privileged user, is rendered. This issue is fixed in version 4.34.0.

Published Oct 20, 2026 · Updated Oct 20, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: GitHub_M

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
  • Technical severity (medium)+3
  • CISA SSVC: exploitation "poc"+5

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
—
No EPSS score.
Affects
Apostrophecms
Apostrophe
CVSS base
5.4
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
Proof of concept
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.

  1. Identify exposed assets running the affected vendor/product/version combinations (Apostrophecms Apostrophe).
  2. No fix documented in the sources: reduce exposure and monitor the vendor advisory.
  3. Exploitation requires user interaction: tighten email/web filtering and warn affected users.
  4. 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.

VendorProductVersionsStatusSource
Apostrophecms Apostrophe version < 4.34.0 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
Low
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.

ScoreVersionSeverityExpl.ImpactScored by
5.4 CVSS 3.1 Medium 2.3 2.7 security-advisories@github.com via NIST National Vulnerability Database
5.4 CVSS 3.1 Medium — — GitHub_M via CVE Program (cve.org) e CISA ADP
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N (score shown at the top: security-advisories@github.com)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-79 · Cross-site Scripting (XSS)

Other CVEs with this weakness →

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
  • Source status changed · Received → Deferred
    Oct 20, 2026 · NIST National Vulnerability Database
  • Affected products added · apostrophecms/apostrophe
    Oct 20, 2026 · CVE Program (cve.org) e CISA ADP
  • SSVC assessment updated
    Oct 20, 2026 · CVE Program (cve.org) e CISA ADP
  • Record published
    Oct 20, 2026
  • CVSS changed · 5.4
    Oct 20, 2026 · NIST National Vulnerability Database
  • Source status changed · → Received
    Oct 20, 2026 · NIST National Vulnerability Database
  • Record created in this database
    Oct 20, 2026 · Alertas do Telegram
  • CVE published
    Oct 20, 2026 · GitHub_M

Source activity

Repeated readings are counted rather than listed.

  • 1× References added · Oct 20, 2026 – Oct 20, 2026
  • 1× Official description updated · Oct 20, 2026 – Oct 20, 2026

References

4 on the record

Elsewhere on this site

Apostrophecms
every CVE for this vendor
Cross-site scripting
same class
CWE-79
other pages naming this weakness

Related CVEs (same products)

  • CVE-2026-113711 ApostropheCMS: Unauthenticated resource exhaustion via pre-auth aposBigUpload processing in @apostrophecms/import-export 11h
  • CVE-2026-113710 ApostropheCMS: No Attempt Throttling on Authenticated Password-Change Endpoint Enables Unlimited Current-Password Guessing 11h
  • CVE-2026-113668 ApostropheCMS: :_id/locales REST route omits the public-API authorization gate its sibling read routes enforce (unauthenticated doc-existence + locale metadata disclosure) 11h
  • CVE-2026-113669 ApostropheCMS: Cross-domain session token in URL confers session takeover 11h
  • CVE-2026-113667 ApostropheCMS: CAPTCHA response token not URL-encoded 11h
  • CVE-2026-113666 ApostropheCMS: Authenticated projection-exclusion prototype-member deletion in @apostrophecms/db-connect causes process-wide denial of service 11h

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 FIRST EPSS score.
  • 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-2026-112958 is "ApostropheCMS: Stored XSS via Unescaped Widget Style Attribute Serialization", rated Medium. It affects Apostrophe (Apostrophecms); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 5.4 describes technical severity. 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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