CVE-2021-3163

Name: CVE-2021-3163
Creator: NVD / NIST
Published: 2021-04-12T21:15:14.34+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 6.1/10EPSS 1.31%

Last modified Jun 17, 2026

CVE-2021-3163 is a medium-severity vulnerability rated 6.1/10 on the CVSS scale. A vulnerability in the HTML editor of Slab Quill 4.8.0 allows an attacker to execute arbitrary JavaScript by storing an XSS payload (a crafted onloadstart attribute of an IMG element) in a text field. Note: Researchers have claimed that this issue is not within the product itself, but is intended behavior in a web browser. EPSS estimates a 1.31% chance of exploitation in the next 30 days.

Description

A vulnerability in the HTML editor of Slab Quill 4.8.0 allows an attacker to execute arbitrary JavaScript by storing an XSS payload (a crafted onloadstart attribute of an IMG element) in a text field. Note: Researchers have claimed that this issue is not within the product itself, but is intended behavior in a web browser

Metrics

CVSS 3.1

6.1/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

EPSS Probability

1.31%

67.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-79

Affected Software

Vendor	Product	Versions
Slab	Quill	4.8.0

References

https://burninatorsec.blogspot.com/2021/04/cve-2021-3163-xss-slab-quill-js.htmlExploit, Third Party Advisory
https://github.com/quilljs/quill/issues/3273Broken Link, Issue Tracking, Third Party Advisory
https://github.com/quilljs/quill/issues/3364Exploit, Issue Tracking, Third Party Advisory
https://quilljs.comProduct
https://burninatorsec.blogspot.com/2021/04/cve-2021-3163-xss-slab-quill-js.htmlExploit, Third Party Advisory
https://github.com/quilljs/quill/issues/3273Broken Link, Issue Tracking, Third Party Advisory
https://github.com/quilljs/quill/issues/3364Exploit, Issue Tracking, Third Party Advisory
https://quilljs.comProduct

Timeline

Published: Apr 12, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-3163?

How severe is CVE-2021-3163?

CVE-2021-3163 has a CVSS score of 6.1/10 (MEDIUM severity). The EPSS model estimates a 1.31% probability of exploitation in the next 30 days.

How do I fix CVE-2021-3163?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-3163?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST