What’s Vulnerable › Vulnerabilities

CVE-2021-40100

• Severity: medium (CVSS 5.4 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-09-24 · updated 2026-06-17
• Weakness: CWE-79

Description

An issue was discovered in Concrete CMS through 8.5.5. Stored XSS can occur in Conversations when the Active Conversation Editor is set to Rich Text.

Affected products

• Concrete CMS: through 8.5.5

References

• https://documentation.concretecms.org/developers/introduction/version-history/856-release-notes
• https://hackerone.com/reports/616770
• https://documentation.concretecms.org/developers/introduction/version-history/856-release-notes
• https://hackerone.com/reports/616770

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