What’s Vulnerable › Vulnerabilities

CVE-2026-55090: Etherpad: Stored XSS in HTML export via unescaped attribute-pool values

• Severity: medium (CVSS 5.3 v4.0)
• 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: 2026-08-19 · updated 2026-09-09
• Weakness: CWE-79

Description

Etherpad is a real-time collaborative editor. Prior to 3.3.0, getHTMLFromAtext in src/node/utils/ExportHtml.ts interpolates values from the exportHtmlAdditionalTagsWithData plugin hook into span data attributes without HTML attribute escaping. A pad editor can place an attacker-controlled value into the attribute pool through moveOpsToNewPool and AttributePool.putAttrib. When a bundled plugin such as ep_font_color or ep_font_size registers the hook, opening the resulting HTML export causes the value to execute as stored cross-site scripting in the Etherpad origin. This issue is fixed in version 3.3.0.

Affected products

• etherpad: before 3.3.0

References

• https://github.com/ether/etherpad/commit/86c56cf827dd6e5ff1b6cd3760f87adc47f58bb1
• https://github.com/ether/etherpad/pull/7905
• https://github.com/ether/etherpad/releases/tag/v3.3.0
• https://github.com/ether/etherpad/security/advisories/GHSA-2jp7-wwpg-3p9w

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