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Medium, CVSS 4.2amended

Cross-site Scripting in quill

CVE-2021-3163GHSA-4943-9vgg-gr5r

What to do

Vendor response not established. Follow the primary source's mitigation guidance and check back for a fix.

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

  • npm quill

    Affected
    <= 1.3.7
    Fixed in
    no fixed version recorded

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
4.2 · CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:N
EPSS
  • CVE-2021-3163: 1.31% estimated exploitation activity in the next 30 days; percentile 70.69 (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.

A vulnerability in the HTML editor of Slab Quill allows an attacker to execute arbitrary JavaScript by storing an XSS payload (a crafted onloadstart attribute of an IMG element) in a text field. No patch exists and no further releases are planned. This CVE is disputed. Researchers have claimed that this issue is not within the product itself, but is intended behavior in a web browser. More information can be found here.

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 2 · amended ·

    Amended from ghsa record GHSA-4943-9vgg-gr5r

  2. Revision 1 · created ·

    Published from osv record GHSA-4943-9vgg-gr5r

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-2021-3163

Advisory: Cross-site Scripting in quill
IDs: CVE-2021-3163, GHSA-4943-9vgg-gr5r
Record: https://patchnext.com/advisories/cve-2021-3163 (revision 2, source checked 26 Oct 2026, 12:31 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.2)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor response not established. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm quill: affected <= 1.3.7

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

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on quill.
- 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-4943-9vgg-gr5r (OSV record GHSA-4943-9vgg-gr5r lists affected ranges: npm quill >=0 <=1.3.7)
- Verified: https://github.com/advisories/GHSA-4943-9vgg-gr5r (GitHub-reviewed advisory GHSA-4943-9vgg-gr5r lists affected ranges: npm quill >=0 <=1.3.7)

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