Preact, a lightweight web development framework, JSON serialization protection to prevent Virtual DOM elements from being constructed from arbitrary JSON. A regression introduced in Preact 10.26.5 caused this protection to be softened. In applications where values from JSON payloads are assumed to be strings and passed unmodified to Preact as children, a specially-crafted JSON payload could be constructed that would be incorrectly treated as a valid VNode. When this chain of failures occurs it can result in HTML injection, which can allow arbitrary script execution if not mitigated by CSP or other means. Applications using affected Preact ver
Versions of `preact` 10.x on prerelease tags alpha and beta prior to 10.0.0-beta.1 are vulnerable to HTML Injection. Due to insufficient input validation the package allows attackers to inject JavaScript objects as virtual-dom nodes, which may lead to Cross-Site Scripting. This requires user input parsed with `JSON.parse()` to be passed directly into JSX without sanitization.
## Recommendation
Upgrade to version 10.0.0-beta.1.