A critical protection mechanism failure in the Scriban template engine allows unauthenticated attackers to bypass sandbox policies and access unauthorized object members via cached template contexts.

The vulnerability stems from improper caching of TypedObjectAccessor where MemberFilter changes are ignored. An unauthenticated attacker can exploit this to access filtered properties and fields by reusing a TemplateContext after its security policy has been tightened.

This flaw permits attackers to circumvent intended sandbox restrictions, leading to unauthorized information disclosure or potential escalation of privileges. With a CVSS score of 9.1, the vulnerability represents a significant risk to the confidentiality and integrity of applications relying on Scriban for template isolation.

Immediate Action: Update the scriban and Scriban.Signed packages to version 7.0.0 or later.

Proactive Monitoring: Monitor for anomalous access patterns within the template rendering engine, particularly those involving frequent context reuse or unexpected data access.

Compensating Controls: Ensure that TemplateContext instances are explicitly cleared or recreated between distinct security contexts to prevent cross-request pollution.

Public Exploit Available: No

Security teams must treat this vulnerability with high urgency. Upgrading to the patched version is necessary to restore the integrity of the sandbox protection mechanism. Organizations should verify their dependency trees to ensure all instances of the affected library are updated.