Cve 2026 35209

Prototype Pollution in defu's Defaults Argument via `__proto__` Key (CVE-2026-35209)

CVE-2026-35209 is a high-severity prototype pollution vulnerability in the `defu` JavaScript library (versions prior to 6.1.5) that allows attackers to inject arbitrary properties onto `Object.prototype` by passing a `__proto__` key in the defaults argument. The vulnerability was present in the `blog-site` project's dependency tree and was resolved by upgrading `defu` to 6.1.5 and adding an explicit `overrides` entry to prevent transitive re-introduction of the vulnerable version.