CVE-2025-27108: DOM Expressions has a Cross-Site Scripting (XSS) vulnerability due to improper use of string.replace

[!NOTE] This advisory was originally emailed to community@solidjs.com by @nsysean.

To sum it up, the use of javascript’s .replace() opens up to potential XSS vulnerabilities with the special replacement patterns beginning with $.

Particularly, when the attributes of Meta tag from solid-meta are user-defined, attackers can utilise the special replacement patterns, either $' or `$`` to achieve XSS.

The solid-meta package has this issue since it uses useAffect and context providers, which injects the used assets in the html header. “dom-expressions” uses .replace() to insert the assets, which is vulnerable to the special replacement patterns listed above.

This effectively means that if the attributes of an asset tag contained user-controlled data, it would be vulnerable to XSS. For instance, there might be meta tags for the open graph protocol in a user profile page, but if attackers set the user query to some payload abusing .replace(), then they could execute arbitrary javascript in the victim’s web browser. Moreover, it could be stored and cause more problems.