Information disclosure through Python's "format" functionality in Zope AccessControl

Vulnerability Description

AccessControl provides a general security framework for use in Zope. Python's "format" functionality allows someone controlling the format string to "read" objects accessible (recursively) via attribute access and subscription from accessible objects. Those attribute accesses and subscriptions use Python's full blown `getattr` and `getitem`, not the policy restricted `AccessControl` variants `_getattr_` and `_getitem_`. This can lead to critical information disclosure. `AccessControl` already provides a safe variant for `str.format` and denies access to `string.Formatter`. However, `str.format_map` is still unsafe. Affected are all users who allow untrusted users to create `AccessControl` controlled Python code and execute it. A fix has been introduced in versions 4.4, 5.8 and 6.2. Users are advised to upgrade. There are no known workarounds for this vulnerability.

References

• https://github.com/zopefoundation/AccessControl/security/advisories/GHSA-8xv7-89vj-q48c
• https://github.com/zopefoundation/AccessControl/commit/6bc32692e0d4b8d5cf64eae3d19de987c7375bc9