Improper Assets Management (OWASP API9:2023) in Grape usually manifests as 'Zombie APIs'—legacy versions (e.g., /v1/) left active despite having weaker security controls than the current production version. Attackers target these unmaintained endpoints to bypass modern authentication or rate-limiting. To secure Grape, you must implement strict versioning lifecycles and ensure environment-specific endpoints are never mounted in production.

The Vulnerable Pattern

class API::Root < Grape::API
  # VULNERABLE: Mounting legacy versions and debug tools without lifecycle management
  mount API::V1::Base # Legacy: lacks MFA and modern rate limiting
  mount API::V2::Base # Current: secure
VULNERABLE: Exposing internal documentation or debug tools based on loose env checks
mount API::Internal::Debug if ENV[‘ENABLE_DEBUG’]
end

The Secure Implementation

The fix involves three core strategies: 1. API Sunset Policy: Instead of leaving old routes active, use a 'before' block to return a 410 Gone status, effectively killing the attack surface while informing clients. 2. Header-based Versioning: Using 'using: :header' instead of URL path versioning makes it harder for automated scanners to discover legacy endpoints. 3. Strict Environment Isolation: Use Rails.env checks rather than custom environment variables to ensure that sensitive internal tools or staging assets are physically excluded from the production route tree.

class API::Root < Grape::API
  # SECURE: Explicitly decommissioning v1 to prevent 'Zombie API' usage
  namespace :v1 do
    before { error!({ error: 'API version v1 is deprecated. Please migrate to v2.' }, 410) }
  end
SECURE: Enforcing versioning via headers and strict mounting
version ‘v2’, using: :header, vendor: ‘secure_app’
mount API::V2::Base
SECURE: Hard-coded environment restriction for internal assets
if Rails.env.development?
mount API::Internal::Debug
end
end