Advisories for Npm/@Builder.io/Qwik-City package

2026

Qwik City has array method pollution in FormData processing allows type confusion and DoS

Summary Qwik City improperly inferred arrays from dotted form field names during FormData parsing. By submitting mixed array-index and object-property keys for the same path, an attacker could cause user-controlled properties to be written onto values that application code expected to be arrays. Description When processing application/x-www-form-urlencoded or multipart/form-data requests, Qwik City converted dotted field names such as items.0 and items.1 into nested structures. If a path was interpreted as …

Qwik SSR XSS via Unsafe Virtual Node Serialization

Description A Cross-site Scripting (CWE-79) vulnerability in Qwik.js' server-side rendering virtual attribute serialization allows a remote attacker to inject arbitrary web scripts into server-rendered pages via virtual attributes. Successful exploitation permits script execution in a victim's browser in the context of the affected origin. This affects qwik-city before version 1.19.0. This has been patched in qwik-city version 1.19.0.

Qwik City Open Redirect via fixTrailingSlash

Description An Open Redirect (CWE-601) vulnerability in Qwik City's default request handler middleware allows a remote attacker to redirect users to arbitrary protocol-relative URLs. Successful exploitation permits attackers to craft convincing phishing links that appear to originate from the trusted domain but redirect the victim to an attacker-controlled site. This affects qwik-city before version 1.19.0. This has been patched in qwik-city version 1.19.0.

Prototype Pollution via FormData Processing in Qwik City

A Prototype Pollution vulnerability exists in the formToObj() function within @builder.io/qwik-city middleware. The function processes form field names with dot notation (e.g., user.name) to create nested objects, but fails to sanitize dangerous property names like proto, constructor, and prototype. This allows unauthenticated attackers to pollute Object.prototype by sending crafted HTTP POST requests, potentially leading to privilege escalation, authentication bypass, or denial of service.

2025
2023