Hydra is a framework for elegantly configuring complex applications. From 1.2.0 until 1.3.0 and 1.4.0.dev10, the hydra-optuna-sweeper package accepts a configuration-controlled dotted path in hydra.sweeper.custom_search_space, resolves it with hydra.utils.get_method(), and later invokes the returned callable in the Hydra controller process. Because get_method() is a trusted-input lookup helper and does not apply the execution policy used by instantiate(), an attacker who controls Optuna sweep configuration or command-line overrides can select importable Python code for execution with the application's privileges, including bypassing a trusted execution whitelist on affected Hydra 1.4 development releases. This issue is fixed in versions 1.3.0 and 1.4.0.dev10.

Affected: PyPI: hydra-optuna-sweeper

## Summary

`hydra-optuna-sweeper` accepted a configuration-controlled dotted path in `hydra.sweeper.custom_search_space`, resolved it with the lower-level `hydra.utils.get_method()` API, and later invoked the returned callable.

Hydra's object-lookup helpers intentionally trust their input and do not apply the execution policy used by `instantiate()` and logging configuration. As a result, untrusted Optuna multirun configuration could select installed Python code for execution in the Hydra controller process.

## Impact

Exploitation requires control of an application's Optuna sweep configuration or command-line overrides and an importable callable in the application's environment. Selected code runs with the privileges of the application.

On affected Hydra 1.4 development releases, this path bypasses an execution whitelist provided by trusted application code. Hydra 1.3 has no execution-whitelist security boundary; there, the same change restores the legacy blocklist as defense in depth.

## Fix

The Optuna sweeper now resolves the configured callback through `hydra.utils.instantiate()` as a partial callable. On Hydra 1.4, the active execution whitelist therefore authorizes the callback before use. On Hydra 1.3, the legacy blocklist is applied as defense in depth.

The public `get_object()`, `get_method()`, `get_static_method()`, and `get_class()` helpers remain lower-level trusted-input APIs. Their documentation now warns against passing values derived from untrusted con…