Why this article exists
Security advisories often sound more alarming than they actually are. When developers see a CVE number, the first reaction is often uncertainty: is this critical, is my application exposed, do I need to worry?
CVE-2026-25148 was reported and fixed in Qwik 1.19.0. This article exists to explain what was affected, what was not, and what action is realistically required.
What is a CVE?
CVE stands for Common Vulnerabilities and Exposures. It is a public identifier assigned to a real, documented security vulnerability.
A CVE is not a rumor, not speculation, and not marketing. It is a reference that allows security tools, auditors, and developers to talk about the same issue using a shared identifier.
What was the vulnerability?
CVE-2026-25148 is a Cross-Site Scripting (XSS) vulnerability that affected Qwik applications using server-side rendering (SSR) prior to version 1.19.0.
The issue was related to how Qwik internally serialized certainvirtual attributes when generating HTML on the server. In very specific scenarios, user-influenced data could end up being injected into the rendered HTML without proper neutralization.
If exploited, this could allow an attacker to inject JavaScript code that would execute in the browser of a visiting user.
Why SSR matters here
In server-side rendering, HTML is generated before it reaches the browser. This means the server must be extremely careful when transforming dynamic values into markup.
Qwik, like all SSR frameworks, performs internal serialization steps that developers do not explicitly control. This vulnerability existed in that internal layer, not in typical user-written application code.
Who is actually affected?
An application could only be affected if all of the following conditions were true:
- Server-side rendering was enabled
- The application was running a version of Qwik prior to 1.19.0
- User-controlled data flowed into virtual attributes handled by the vulnerable serialization path
This significantly limits the real-world exposure. Most applications were not trivially exploitable, and no widespread exploitation has been reported.
What changed in Qwik 1.19.0?
Qwik 1.19.0 includes a fix that ensures virtual attributes are properly handled during SSR serialization. The change is internal and does not require application-level code changes.
This is a typical example of a framework-level security fix: transparent for most developers, but critical to apply.
📦 Related release
This security fix is part of the broader Qwik 1.19.0 release. For a complete overview of performance, SSR, and DX improvements, read: Qwik 1.19.0: a quiet but strategic update.
Do I need to change my code?
In almost all cases, no. If you are not manually constructing unsafe HTML strings or bypassing framework safeguards, updating Qwik is sufficient.
If your application uses Qwik City for routing, SSR, loaders, or actions, make sure to update both @builder.io/qwik and@builder.io/qwik-city to keep versions aligned.
Should I be worried?
No panic is warranted. The vulnerability was identified, documented, and fixed. That is exactly how healthy open-source ecosystems operate.
The correct response is not fear, but maintenance: keep dependencies reasonably up to date and understand what changes actually mean.
What this says about Qwik
The fact that this vulnerability was publicly tracked, assigned a CVE, and fixed without breaking applications is a positive signal.
Security issues are inevitable in complex systems. Transparent handling and timely fixes are what matter.
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Continue learning Qwik
Understanding how Qwik handles SSR, serialization, and resumability helps you reason about both performance and security.