Issue name

CSS injection (reflected)

Typical severity

Medium

Issue description

CSS injection vulnerabilities arise when an application imports a style sheet from a user-supplied URL, or embeds user input in CSS blocks without adequate escaping. They are closely related to cross-site scripting (XSS) vulnerabilities but often trickier to exploit.

Being able to inject arbitrary CSS into the victim's browser may enable various attacks, including:

Issue remediation

Ensure that user input is adequately escaped before embedding it in CSS blocks, and consider using a whitelist to prevent loading of arbitrary style sheets.

References

Vulnerability classifications

Web intro