The high-level diff API fails to restrict the `--no-index` option, which allows attackers to read arbitrary filesystem paths as repository operands. By combining `--no-index` with `-I/--ignore-matching-lines`, an attacker can create a content-dependent Boolean oracle. This technique enables the recovery of single-line secrets from local files by analyzing the difference between success and error responses. This issue can be exploited by a remote attacker to gain unauthorized access to protected information.