svelte performance oriented web framework. Prior to 5.51.5, in server-side rendering, attribute spreading on elements (e.g. <div {…attrs}>) enumerates inherited properties from the objects prototype chain rather than only own properties. In environments where Object.prototype has already been polluted — a precondition outside of Sveltes control — this can cause unexpected attributes to appear in SSR output or cause SSR to throw errors. Client-side rendering is not affected. This vulnerability is fixed in 5.51.5.
Weakness
The product receives input from an upstream component that specifies multiple attributes, properties, or fields that are to be initialized or updated in an object, but it does not properly control which attributes can be modified.
Extended Description
If the object contains attributes that were only intended for internal use, then their unexpected modification could lead to a vulnerability. This weakness is sometimes known by the language-specific mechanisms that make it possible, such as mass assignment, autobinding, or object injection.
Potential Mitigations
- If available, use features of the language or framework that allow specification of allowlists of attributes or fields that are allowed to be modified. If possible, prefer allowlists over denylists.
- For applications written with Ruby on Rails, use the attr_accessible (allowlist) or attr_protected (denylist) macros in each class that may be used in mass assignment.