# Improper Restriction of XML External Entity Reference in Plone

Advisory record · `GHSA-2c8c-84w2-j38j`

- **Identifiers:** `GHSA-2c8c-84w2-j38j` · `CVE-2020-28736` · `PYSEC-2020-248` · `PYSEC-2026-2879` · `PYSEC-2026-2882` · `PYSEC-2026-2885` · `PYSEC-2026-735`
- **State:** Confirmed
- **Severity:** CVSS 8.8 High
- **Critical:** No
- **Weakness (CWE):** [CWE-611](https://cwe.mitre.org/data/definitions/611.html)
- **Tags:** [XML external entities (XXE)](https://agentprime.io/advisories/tag/xxe.md)
- **Published:** 7 Apr 2021
- **Updated:** 13 Jul 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 7 Apr 2021, 21:14 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `plone` (PyPI): affected `<5.2.3`; fixed in `5.2.3`
- `plone-app-event` (PyPI): affected `<3.2.10`; fixed in `3.2.10`
- `plone-app-theming` (PyPI): affected `<4.1.6`; fixed in `4.1.6`
- `plone-app-dexterity` (PyPI): affected `<2.6.8`; fixed in `2.6.8`
- `plone-supermodel` (PyPI): affected `<1.6.3`; fixed in `1.6.3`

## 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

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

- **CISA KEV:** Not listed.
- **EPSS:** 0.015, the 73rd percentile, on 12 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 15:01 UTC: First seen by agentprime
- 31 Oct 2026, 15:01 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-2c8c-84w2-j38j)

## Sources

- [GitHub Advisory Database: GHSA-2c8c-84w2-j38j](https://github.com/advisories/GHSA-2c8c-84w2-j38j)
- [OSV: GHSA-2c8c-84w2-j38j](https://osv.dev/vulnerability/GHSA-2c8c-84w2-j38j)
- <https://nvd.nist.gov/vuln/detail/CVE-2020-28736>
- <https://github.com/plone/Products.CMFPlone/issues/3209>
- <https://dist.plone.org/release/5.2.3/RELEASE-NOTES.txt>
- <https://github.com/advisories/GHSA-2c8c-84w2-j38j>
- <https://github.com/pypa/advisory-database/tree/main/vulns/plone/PYSEC-2020-248.yaml>
- <https://www.misakikata.com/codes/plone/python-en.html>

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-2c8c-84w2-j38j>, 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-2c8c-84w2-j38j/>. Everything for agents: <https://agentprime.io/llms.txt>.