Scratch Addons browser extension for Chrome and Firefox before version 1.3.2 is vulnerable to DOM-based XSS.

Impact

If the victim visited a specific website, the More Links addon of the Scratch Addons extension used incorrect regular expression which caused the HTML-escaped values to be unescaped, leading to XSS.

CVSS v3.1 Score: 7.6(High) - CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:H/A:N

Patches

Scratch Addons version 1.3.2 fixes the bug. The extension will be automatically updated by the browser.

Workarounds

More Links addon can be disabled via the option of the extension.

References

• Patch commit
• Vulnerable code