CVE-2020-28734 — plone
HIGHCVE-2020-28734 is a high-severity (CVSS 8.8) XML External Entity (XXE) vulnerability in plone. A fix is available for plone — see the affected versions and patch details below.
Improper Restriction of XML External Entity Reference in Plone
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2020-28734 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
plone🐍plone-app-event🐍plone-app-theming🐍plone-app-dexterity🐍plone-supermodelReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Plone before 5.2.3 allows XXE attacks via a feature that is explicitly only available to the Manager role.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | plone | all versions | 5.2.3pip install --upgrade 'plone==5.2.3' |
| 🐍PyPI | plone-app-event | all versions | 3.2.10pip install --upgrade 'plone-app-event==3.2.10' |
| 🐍PyPI | plone-app-theming | all versions | 4.1.6pip install --upgrade 'plone-app-theming==4.1.6' |
| 🐍PyPI | plone-app-dexterity | all versions | 2.6.8pip install --upgrade 'plone-app-dexterity==2.6.8' |
| 🐍PyPI | plone-supermodel | all versions | 1.6.3pip install --upgrade 'plone-supermodel==1.6.3' |
Affected Products
ploneploneDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for plone, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update plone to 5.2.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-28734 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Frequently Asked Questions
Is CVE-2020-28734 in your dependencies?
Find it across PyPI, including transitive dependencies.