Prototype pollution in ApostropheCMS query parsing enables XSS
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- Required
- Attack complexity
- Low
- Impact type
- Cross-site scripting
- Confidentiality · integrity · availability
- Low · Low · None
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-79.
Summary
The apostrophe npm package of ApostropheCMS is affected before 4.33.0. Its query parser, apos.http.parseQuery, accepts the __proto__, constructor and prototype keys, which allows prototype pollution in the browser (CWE-1321). An unauthenticated attacker can send a crafted link that, when an authenticated user loads a page with the admin bundle, pollutes prototypes and reaches an unsafe DOM sink to run script in the victim's session (CWE-79). Anonymous visitors do not load the affected admin context.
Written with Claude Haiku 5.5 from the sources below · 2026-10-29
Description from the CNA
ApostropheCMS is an open-source Node.js content management system. Prior to 4.33.0, an unauthenticated attacker can send a crafted link whose query string is automatically parsed by apos.http.parseQuery when an authenticated victim loads a page with the admin bundle. The parser accepts the special __proto__, constructor, and prototype path keys, allowing browser prototype mutation that can reach an unsafe DOM sink and execute script in the victim's session; anonymous visitors do not load the affected admin context. This issue is fixed in version 4.33.0.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| apostrophecms | apostrophe | before 4.33.0 | 4.33.0 | Patch available | CNA |
| — | apostrophe (npm) | before 4.33.0 | 4.33.0 | Patch available | GHSA-m2m5-rw3w-cwmj |
- apostrophe Vendorapostrophecms Affected before 4.33.0 Fixed in 4.33.0 Patch available CNA
- apostrophe (npm) Vendor— Affected before 4.33.0 Fixed in 4.33.0 Patch available GHSA-m2m5-rw3w-cwmj
CPE names Threatist (inferred) · 1
Inferred from how NVD named this product before; not given by a source.
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:apostrophecms:apostrophecms:*:*:*:*:*:*:*:* | — | — | apostrophecms |
- cpe:2.3:a:apostrophecms:apostrophecms:*:*:*:*:*:*:*:* Versions — — ·apostrophecms
Remediation
Upgrade the apostrophe npm package to version 4.33.0, which fixes this issue.
Written with Claude Haiku 5.5 from the sources below · 2026-10-29
- Fix · CNA apostrophe (apostrophecms) Fixed in 4.33.0
- Fix · GHSA-m2m5-rw3w-cwmj apostrophe (npm) Fixed in 4.33.0 Advisory →
Timeline
- 2026-10-20 Threatist record created from CVE-2026-113659
- 2026-10-21 Alias added: GHSA-m2m5-rw3w-cwmj
- 2026-10-21 Fix available: npm/[email protected] · GHSA-m2m5-rw3w-cwmj
- 2026-10-21 CVSS score added · GHSA-m2m5-rw3w-cwmj
- 2026-10-21 Weakness changed · GHSA-m2m5-rw3w-cwmj
- 2026-10-21 5 new references · GHSA-m2m5-rw3w-cwmj
- 2026-10-22 Priority changed: MEDIUM → LOW
- 2026-10-28 CISA SSVC decision points changed
References
Other 5
- https://github.com/apostrophecms/apostrophe/security/advisories/GHSA-m2m5-rw3w-cwmj
- https://github.com/apostrophecms/apostrophe/commit/9500b8b0e1d630d5e07fbb5fd2c25ed0943845ce
- https://github.com/apostrophecms/apostrophe/commit/f84fd41cbf6c22eb8d0008fc9c25df1f7130b350
- https://github.com/apostrophecms/apostrophe/releases/tag/[email protected]
- https://github.com/apostrophecms/apostrophe
More apostrophecms vulnerabilities
- TI-2026-25223 ApostropheCMS has Arbitrary File Write (Zip Slip / Path Traversal) in Import-Export Gzip Extraction CVSS 3.1CRITICAL 10.0
- TI-2026-32848 Apostrophe has default XSS via `xmp` raw-text passthrough in `sanitize-html` CVSS 3.1CRITICAL 9.3
- TI-2026-38664 @apostrophecms/seo Vulnerable to Stored XSS via Unsanitized Google Analytics / GTM ID Injected into Script Tag CVSS 3.1HIGH 8.7
- TI-2026-27673 ApostropheCMS: Stored XSS in SEO Fields Leads to Authenticated API Data Exposure in ApostropheCMS CVSS 3.1HIGH 8.7
- TI-2026-76992 Unauthenticated resource exhaustion via ApostropheCMS import routes CVSS 3.1HIGH 7.5
- TI-2026-76974 ApostropheCMS leaves rejected CSV uploads in temporary directory CVSS 3.1HIGH 7.5
Sources
- CVE-2026-113659 · CVE Program
- CVE-2026-113659 · NVD
- FIRST EPSS
- GHSA-m2m5-rw3w-cwmj · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences