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Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')


Severity Medium
Score 6.1/10


Nunjucks is a full featured templating engine for JavaScript. Versions 2.4.2 and lower have a cross site scripting (XSS) vulnerability in autoescape mode. In autoescape mode, all template vars should automatically be escaped. By using an array for the keys, such as `name[]=<script>alert(1)</script>`, it is possible to bypass autoescaping and inject content into the DOM.

  • LOW
  • LOW
  • NONE
  • LOW
  • NONE

CWE-79 - Cross Site Scripting

Cross-Site Scripting, commonly referred to as XSS, is the most dominant class of vulnerabilities. It allows an attacker to inject malicious code into a pregnable web application and victimize its users. The exploitation of such a weakness can cause severe issues such as account takeover, and sensitive data exfiltration. Because of the prevalence of XSS vulnerabilities and their high rate of exploitation, it has remained in the OWASP top 10 vulnerabilities for years.

Advisory Timeline

  • Published