Impact

In Nunjucks versions prior to version 3.2.4, it was possible to bypass the restrictions which are provided by the autoescape functionality. If there are two user-controlled parameters on the same line used in the views, it was possible to inject cross site scripting payloads using the backslash \ character.

Example

If the user-controlled parameters were used in the views similar to the following:

<script>
let testObject = { lang: '{{ lang }}', place: '{{ place }}' };
</script>

It is possible to inject XSS payload using the below parameters:

https://<application-url>/?lang=jp\&place=};alert(document.domain)//

Patches

The issue was patched in version 3.2.4.

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=1825980

References

• GHSA-x77j-w7wf-fjmw
• mozilla/nunjucks#1437
• mozilla/nunjucks@ec16d21
• https://bugzilla.mozilla.org/show_bug.cgi?id=1825980
• https://github.com/mozilla/nunjucks/releases/tag/v3.2.4