What’s Vulnerable › Vulnerabilities

CVE-2020-8294

• Severity: medium (CVSS 5.4 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.9% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-02-03 · updated 2026-06-17
• Weakness: CWE-79

Description

A missing link validation in Nextcloud Server before 20.0.2, 19.0.5, 18.0.11 allows execution of a stored XSS attack using Internet Explorer when saving a 'javascript:' URL in markdown format.

Affected products

• Nextcloud Server: before 18.0.11; from 19.0.0 before 19.0.5; from 20.0.0 before 20.0.2 — fixed in 18.0.11, 19.0.5, 20.0.2

How to fix

Upgrade to a fixed version: Nextcloud Server 18.0.11, 19.0.5, 20.0.2. Check the vendor advisory for mitigations.

References

• https://hackerone.com/reports/1023787
• https://nextcloud.com/security/advisory/?id=NC-SA-2021-002
• https://hackerone.com/reports/1023787
• https://nextcloud.com/security/advisory/?id=NC-SA-2021-002

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