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Critical, CVSS 9.6

Cross-site Scripting (XSS) in Eclipse Theia

CVE-2020-27224GHSA-gcm9-cc3r-c6vj

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (@theia/preview 1.3.0), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
9.6 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
EPSS
  • CVE-2020-27224: 2.59% estimated exploitation activity in the next 30 days; percentile 85.33 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

In Eclipse Theia versions up to and including 1.2.0, the Markdown Preview (@theia/preview), can be exploited to execute arbitrary code.

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 1 · created ·

    Published from osv record GHSA-gcm9-cc3r-c6vj

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2020-27224

Advisory: Cross-site Scripting (XSS) in Eclipse Theia
IDs: CVE-2020-27224, GHSA-gcm9-cc3r-c6vj
Record: https://patchnext.com/advisories/cve-2020-27224 (revision 1, source checked 24 Oct 2026, 04:13 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.6)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: @theia/preview 1.3.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @theia/preview: affected < 1.3.0; fixed in 1.3.0

## Suggested inspection (read-only)
- `npm ls @theia/preview --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on @theia/preview.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-gcm9-cc3r-c6vj (OSV record GHSA-gcm9-cc3r-c6vj lists affected ranges: npm @theia/preview >=0 <1.3.0 (fixed))

Commands are suggestions: review each one before running it.

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