# CVE-2020-28734: PYSEC-2026-736 - Improper Restriction of XML External Entity Reference in Plone

Source: https://junglewise.ai/threats/cve-2020-28734-improper-restriction-of-xml-external-entity-reference-in-plone  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-02  
License: CC BY 4.0 with a link back

CVE-2020-28734 · Severity: low · CVSS 3.1 · Published 2026-07-02

Improper Restriction of XML External Entity Reference in Plone

Technologies: [plone (PyPI)](https://junglewise.ai/threats/technologies/pypi-plone), [plone-app-theming (PyPI)](https://junglewise.ai/threats/technologies/plone-app-theming), [plone-supermodel (PyPI)](https://junglewise.ai/threats/technologies/plone-supermodel), [plone.app.dexterity (PyPI)](https://junglewise.ai/threats/technologies/plone-app-dexterity), [plone.app.event (PyPI)](https://junglewise.ai/threats/technologies/plone-app-event). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2020-28734 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2020-28734 being exploited in the wild.

**How severe is CVE-2020-28734?** Low severity, with a CVSS score of 3.1, published 2 July 2026.

**Which products and versions are affected?** plone (PyPI) ECOSYSTEM:introduced=0,fixed=5.2.3; plone-app-theming (PyPI) ECOSYSTEM:introduced=0,fixed=4.1.6; plone-supermodel (PyPI) ECOSYSTEM:introduced=0,fixed=1.6.3; plone.app.dexterity (PyPI) ECOSYSTEM:introduced=0,fixed=2.6.8; and 1 more.

**Is there a fix for CVE-2020-28734?** Yes. plone (PyPI): upgrade to 5.2.3 or later; plone-app-theming (PyPI): upgrade to 4.1.6 or later; plone-supermodel (PyPI): upgrade to 1.6.3 or later; plone.app.dexterity (PyPI): upgrade to 2.6.8 or later; plone.app.event (PyPI): upgrade to 3.2.10 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected by CVE-2020-28734?** Check whether you run plone (PyPI), plone-app-theming (PyPI), plone-supermodel (PyPI) or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- plone (PyPI): upgrade to 5.2.3 or later

  ```sh
  pip install "plone>=5.2.3"
  ```

- plone-app-theming (PyPI): upgrade to 4.1.6 or later

  ```sh
  pip install "plone-app-theming>=4.1.6"
  ```

- plone-supermodel (PyPI): upgrade to 1.6.3 or later

  ```sh
  pip install "plone-supermodel>=1.6.3"
  ```

- plone.app.dexterity (PyPI): upgrade to 2.6.8 or later

  ```sh
  pip install "plone.app.dexterity>=2.6.8"
  ```

- plone.app.event (PyPI): upgrade to 3.2.10 or later

  ```sh
  pip install "plone.app.event>=3.2.10"
  ```


## Affected products

- plone (PyPI) ECOSYSTEM:introduced=0,fixed=5.2.3
- plone-app-theming (PyPI) ECOSYSTEM:introduced=0,fixed=4.1.6
- plone-supermodel (PyPI) ECOSYSTEM:introduced=0,fixed=1.6.3
- plone.app.dexterity (PyPI) ECOSYSTEM:introduced=0,fixed=2.6.8
- plone.app.event (PyPI) ECOSYSTEM:introduced=0,fixed=3.2.10

## Identifiers

- CVE-2020-28734
- GHSA-wq6x-g685-w5f2
- PYSEC-2020-246
- PYSEC-2026-2880
- PYSEC-2026-2883
- PYSEC-2026-2886
- PYSEC-2026-736

## Related threats

- [Plone plone.app.dexterity denial of service via excessive field length](https://junglewise.ai/threats/cve-2026-57576-plone-plone-app-dexterity-denial-of-service-via-excessive-field)
- [Plone plone.app.event denial of service in iCalendar import](https://junglewise.ai/threats/cve-2026-55247-plone-plone-app-event-denial-of-service-in-icalendar-import)
- [PYSEC-2026-2889 - Plone Privilege Escallation](https://junglewise.ai/threats/cve-2020-7938-plone-privilege-escallation)
- [PYSEC-2026-2964 - Plone unauthorized member addition vulnerability](https://junglewise.ai/threats/cve-2015-7315-plone-unauthorized-member-addition-vulnerability)
- [PYSEC-2026-2962 - Products.CMFPlone XSS in profile home_page property](https://junglewise.ai/threats/cve-2017-1000482-products-cmfplone-xss-in-profile-home-page-property)