# CVE-2026-126498: WriteFreely before 0.17.3 Stored XSS via Unsanitized Post Slug

Status: published. Published: 2026-11-11. Updated: 2026-11-14.

WriteFreely before 0.17.3 contains a stored cross-site scripting vulnerability that allows authenticated authors to inject HTML by supplying a malicious post slug via the CreatePost API. The raw slug is concatenated into an anchor by augmentReadingDestination() for paid-shortcode posts, executing script for RSS/Atom feed readers, newsletter recipients and ActivityPub viewers.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://github.com/writefreely/writefreely/commit/d7231d81a914f1314a218d5e8fde6e0341391ccd

## Affected products and versions

- Musing Studio / WriteFreely (github.com/writefreely/writefreely): ≥ 0; < 0.17.3 (affected, semver). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 5.1 (medium); CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N; source: CNA: VulnCheck

- CVSS 3.1: 5.4 (medium); CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N; source: CNA: VulnCheck

- CVSS 4.0: 5.1 (medium); CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:L/VI:L/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; source: NVD: disclosure@vulncheck.com

- CVSS 3.1: 5.4 (medium); CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N; source: NVD: disclosure@vulncheck.com

- CISA KEV: No listing in collected sources

- EPSS: 0.23% as of 2026-11-13; percentile 14.23%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-79

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/writefreely/writefreely/security/advisories/GHSA-cwxm-8ch5-j2vh (CNA: VulnCheck; vendor-advisory)

- https://github.com/writefreely/writefreely/commit/d7231d81a914f1314a218d5e8fde6e0341391ccd (CNA: VulnCheck; patch)

- https://github.com/writefreely/writefreely/releases/tag/v0.17.3 (CNA: VulnCheck; release-notes)

- https://github.com/writefreely/writefreely/blob/v0.17.2/postrender.go#L117-L121 (CNA: VulnCheck; technical-description)

- https://github.com/writefreely/writefreely/blob/v0.17.2/database.go#L702-L705 (CNA: VulnCheck; technical-description)

- https://www.vulncheck.com/advisories/writefreely-before-0.17.3-stored-xss-via-unsanitized-post-slug (CNA: VulnCheck; third-party-advisory)

- https://github.com/writefreely/writefreely/blob/v0.17.2/database.go#L702-L705 (disclosure@vulncheck.com)

- https://github.com/writefreely/writefreely/blob/v0.17.2/postrender.go#L117-L121 (disclosure@vulncheck.com)

- https://github.com/writefreely/writefreely/commit/d7231d81a914f1314a218d5e8fde6e0341391ccd (disclosure@vulncheck.com)

- https://github.com/writefreely/writefreely/releases/tag/v0.17.3 (disclosure@vulncheck.com)

- https://github.com/writefreely/writefreely/security/advisories/GHSA-cwxm-8ch5-j2vh (disclosure@vulncheck.com)

- https://www.vulncheck.com/advisories/writefreely-before-0.17.3-stored-xss-via-unsanitized-post-slug (disclosure@vulncheck.com)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-126498; retrieved 2026-11-14; source updated 2026-11-14

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-126498; retrieved 2026-11-13; source updated 2026-11-12

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-126498; retrieved 2026-11-14; source updated Not reported

Revision: 315cef10b8f868921d370b91edc4941ec1a268636e366371dc7f82563a1e6fcc

Canonical: https://y2.dev/cve/CVE-2026-126498

## Agent and API access

Public CVE pages, Markdown, and JSON are free to read without an account or API key.

- Public catalog: https://y2.dev/cve/index.json. Follow nextCursor with the same search, filters, sort, and limit (1–100). A null cursor marks the end.

- WebMCP: search_cve_disclosures, get_cve_disclosure, get_cve_page_markdown, get_y2_cve_access. Available in compatible browsers.

- Cyber API: https://api.y2.dev/api/v2/cyber/cves and https://api.y2.dev/api/v2/cyber/cves/{cveId}.

- Y2 Pro or Elite: create a workspace API key with the intel:cyber scope and send Authorization: Bearer <Y2_API_KEY>. Setup: https://y2.dev/docs/api/create-key.

- x402: Pay per request without an account or API key. Omit Authorization, read the HTTP 402 PAYMENT-REQUIRED challenge, validate its current requirements, and retry with PAYMENT-SIGNATURE through an authorized payment client. These browser tools never make payments. Guide: https://y2.dev/docs/api/x402.

- OpenAPI: https://y2.dev/api/openapi.yaml. Agent access metadata: https://y2.dev/cve/agent.json.

Collected public records only. Check source status for coverage and freshness.