RestrictedPython prior to version 8.4 contains a vulnerability where restricted code can escape the sandbox if a custom import policy or globals expose the standard library string module, the string.Formatter class, a Formatter instance, or a Formatter subclass. The Formatter methods format, get_field, get_value, and vformat perform attribute and item traversal internally without passing through RestrictedPython's safer_getattr protections. This allows restricted code to leverage live object references to access function globals, builtins, file access, or code execution primitives, thereby impacting confidentiality, integrity, and availability. The vulnerability is addressed in version 8.4.

Exploitation of this vulnerability allows restricted code to bypass sandbox restrictions and gain unauthorized access to sensitive information and execution capabilities within the host environment. This can lead to full compromise of confidentiality, integrity, and availability of the affected system running RestrictedPython versions prior to 8.4.

Upgrade to RestrictedPython version 8.4 or later, where this vulnerability is fixed. No other mitigation is indicated or required by the vendor advisory.