# Prototype pollution in json8-merge-patch

Advisory record · `GHSA-8v9x-9xqg-r8mr`

- **Identifiers:** `GHSA-8v9x-9xqg-r8mr` · `CVE-2020-8268`
- **State:** Confirmed
- **Severity:** CVSS 7.5 High
- **Critical:** No
- **Weakness (CWE):** [CWE-20](https://cwe.mitre.org/data/definitions/20.html) · [CWE-471](https://cwe.mitre.org/data/definitions/471.html) · [CWE-1321](https://cwe.mitre.org/data/definitions/1321.html)
- **Tags:** [Prototype pollution](https://agentprime.io/advisories/tag/prototype-pollution.md) · [CWE-20](https://agentprime.io/advisories/tag/cwe-20.md) · [CWE-471](https://agentprime.io/advisories/tag/cwe-471.md)
- **Published:** 10 May 2021
- **Updated:** 8 Nov 2023
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 10 May 2021, 19:17 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `json8-merge-patch` (npm): affected `<1.0.3`; fixed in `1.0.3`

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 7.5 High, CVSS 3.1: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N`, from GitHub Advisory Database

- **CISA KEV:** Not listed.
- **EPSS:** 0.013, the 70th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

This record came from the full history of the GitHub Advisory Database, published 10 May 2021. New records show when each source confirmed them.

## Sources

- [GitHub Advisory Database: GHSA-8v9x-9xqg-r8mr](https://github.com/advisories/GHSA-8v9x-9xqg-r8mr)
- [OSV: GHSA-8v9x-9xqg-r8mr](https://osv.dev/vulnerability/GHSA-8v9x-9xqg-r8mr)
- <https://nvd.nist.gov/vuln/detail/CVE-2020-8268>
- <https://github.com/sonnyp/JSON8/issues/113>
- <https://github.com/sonnyp/JSON8/commit/2e890261b66cbc54ae01d0c79c71b0fd18379e7e#diff-faa7bef039022bc7ca1c613331b2373950ddd3d65ebf25d1699fbdf89773a387>
- <https://hackerone.com/reports/980649>
- <https://www.npmjs.com/package/json8-merge-patch>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-8v9x-9xqg-r8mr>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-8v9x-9xqg-r8mr/>. Everything for agents: <https://agentprime.io/llms.txt>.