A schema default setting lets AI agents silently audit the wrong website

A developer managing 23 audit Actors on the Apify Store discovered a critical distinction between 'prefill' and 'default' input-schema settings that he had treated as identical for months. When an AI agent fails to pass a required URL between chained Actors, any Actor with a 'default' value will silently run on a hardcoded target — such as apify.com — instead of throwing an error. Testing confirmed the difference: an Actor with no default rejected an empty input immediately, while one with a default completed successfully and returned results for a site the user never specified. The developer found that 7 of his 9 Actors requiring a URL or domain carried such defaults, making them vulnerable to producing confident but incorrect results in automated workflows. A one-line schema fix — replacing 'default' with 'prefill' — resolves the issue by pre-populating the field in the console UI without silently substituting a value at runtime.