Executive brief
Builder.io Gen2 SDKs are visual development tools used to create web interfaces across multiple frameworks (React, Vue, Svelte, etc.). A prototype pollution flaw in the content rendering pipeline allows attackers to inject malicious binding keys that corrupt the global Object prototype during page rendering, potentially affecting all subsequent operations and other users' sessions running on the same system.
Technical details
A prototype pollution vulnerability exists in the deep-set helper function used to process content block bindings within the Gen2 SDKs. The vulnerable code fails to validate binding keys before assignment, allowing attackers to craft content blocks containing malicious keys such as __proto__, prototype, or constructor that pollute Object.prototype during rendering. The attack requires network access to provide crafted content blocks to the SDK rendering engine. Successful exploitation enables arbitrary property injection into the global object prototype, potentially leading to code execution or denial of service affecting all subsequent object creation. Multi-tenant environments are particularly at risk, as prototype pollution can cross tenant boundaries during concurrent render operations.
Affected products
- Builder.io Gen2 SDKs through 5.2.11 and 0.25.13
Timeline
- 2026-09-16: disclosed