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.

References

• preactjs/preact#1528
• https://github.com/developit/preact/releases/tag/10.0.0-beta.1
• https://medium.com/dailyjs/exploiting-script-injection-flaws-in-reactjs-883fb1fe36c1
• https://www.npmjs.com/advisories/835