CVE-2021-3163: Slab Quill

Medium severity, CVSS 6.1. EPSS: 1.3% chance of exploitation in the next 30 days.

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

Affected products

• Slab Quill: version 4.8.0 only

Published 2021-04-12. Last modified 2026-06-17.