# CVE-2026-53597: Prompty: Arbitrary code execution via JavaScript frontmatter in TypeScript loader

> Attackers can execute arbitrary JavaScript by crafting malicious .prompty files with executable frontmatter, affecting users of the Prompty TypeScript loader.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 16 Jul 2026
- **Updated:** 18 Jul 2026
- **Also known as:** GHSA-c4gh-rv8h-q9vw

## What is CVE-2026-53597?

CVE-2026-53597 is a high-severity code injection vulnerability in microsoft prompty, published on 16 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

Prompty is a markdown file format (.prompty) for LLM prompts. From 2.0.0-alpha.1 until 2.0.0-beta.3, the @prompty/core TypeScript loader in runtime/typescript/packages/core/src/core/loader.ts used gray-matter without overriding executable js and javascript frontmatter engines, allowing an attacker-controlled .prompty file with ---js frontmatter to execute arbitrary JavaScript during prompt loading. This issue is fixed in version 2.0.0-beta.3.

Weakness: CWE-94 (Improper Control of Generation of Code)

## Which versions are affected by CVE-2026-53597?

2 open source packages ship an affected version, including @prompty/core.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `@prompty/core` | npm | From 2.0.0-alpha.1 | 2.0.0-beta.3 |
| `@prompty/core` | npm | From 2.0.0-alpha.1 | 2.0.0-beta.3 |

## How do I fix CVE-2026-53597?

Upgrade @prompty/core to 2.0.0-beta.3 or later.

## Is CVE-2026-53597 being exploited?

There is no known exploitation of CVE-2026-53597 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-53597 and fix it if it is affected.

What it is: CVE-2026-53597 is a high-severity code injection vulnerability in microsoft prompty, published on 16 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-53597 in the wild and no public exploit code.

Affected packages and fixed versions:
- @prompty/core (npm): affected from 2.0.0-alpha.1; fixed in 2.0.0-beta.3
- @prompty/core (npm): affected from 2.0.0-alpha.1; fixed in 2.0.0-beta.3

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-53597/ (Markdown: https://insights.sbomify.com/CVE-2026-53597/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-53597
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-53597
- OSV: https://osv.dev/vulnerability/CVE-2026-53597

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-53597/
Summaries are generated and may contain mistakes; the official description above is the record.