diff --git a/src/clawbench/runner/run_support/task.py b/src/clawbench/runner/run_support/task.py
index 96c4f6ee..24403b16 100644
--- a/src/clawbench/runner/run_support/task.py
+++ b/src/clawbench/runner/run_support/task.py
@@ -129,6 +129,30 @@ def add_item(item: Any, label: str) -> None:
     return entries, warnings
 
 
+def validate_extra_info_path(task_dir: Path, rel_path: str) -> Path:
+    """Resolve an extra_info path and reject anything outside ``task_dir``.
+
+    A task's ``extra_info[].path`` is untrusted input. Without a guard, an
+    absolute path or one containing ``..`` could make ``copy_extra_info`` read
+    arbitrary host files into the staged my-info dir (which may be shipped in a
+    shareable export). Reject absolute paths and any target whose resolved
+    location — symlinks followed — escapes ``task_dir``. Returns the unresolved
+    ``task_dir / rel_path`` so normal copy semantics are unchanged.
+    """
+    if Path(rel_path).is_absolute():
+        raise ValueError(
+            f"extra_info path must be relative, got absolute: {rel_path!r}"
+        )
+    src = task_dir / rel_path
+    try:
+        src.resolve().relative_to(task_dir.resolve())
+    except ValueError as e:
+        raise ValueError(
+            f"extra_info path escapes the task directory: {rel_path!r}"
+        ) from e
+    return src
+
+
 def copy_extra_info(task: dict, task_dir: Path, personal_info_dir: Path) -> list[str]:
     """Copy extra_info files from the test case into the my-info dir."""
     entries, warnings = normalize_extra_info(task.get("extra_info"))
@@ -138,7 +162,7 @@ def copy_extra_info(task: dict, task_dir: Path, personal_info_dir: Path) -> list
         rel_path = info.get("path")
         if not rel_path:
             continue
-        src = task_dir / rel_path
+        src = validate_extra_info_path(task_dir, rel_path)
         if not src.exists():
             warning = f"extra_info path not found: {src}"
             warnings.append(warning)
diff --git a/tests/test_host_resources.py b/tests/test_host_resources.py
index bd291c90..cf41b962 100644
--- a/tests/test_host_resources.py
+++ b/tests/test_host_resources.py
@@ -6,11 +6,14 @@
 import json
 from pathlib import Path
 
+import pytest
+
 from clawbench.runner.run_support.task import (
     build_instruction,
     copy_extra_info,
     normalize_extra_info,
     prepare_personal_info,
+    validate_extra_info_path,
 )
 from clawbench.utils.paths import ASSET_ROOT, SHARED_ROOT
 
@@ -63,6 +66,39 @@ def test_extra_info_copy_and_instruction_are_host_side(tmp_path: Path) -> None:
     assert "2-day meal plan" in instruction
 
 
+def test_validate_extra_info_path_accepts_valid_relative(tmp_path: Path) -> None:
+    (tmp_path / "info.json").write_text("{}")
+    src = validate_extra_info_path(tmp_path, "info.json")
+    assert src == tmp_path / "info.json"
+
+
+def test_validate_extra_info_path_rejects_absolute(tmp_path: Path) -> None:
+    # Must be rejected. On POSIX "/etc/passwd" trips the is_absolute() guard
+    # ("absolute"); on Windows it isn't absolute (no drive), so it's rejected by
+    # the containment check ("escapes") instead — either way it raises.
+    with pytest.raises(ValueError, match="absolute|escapes"):
+        validate_extra_info_path(tmp_path, "/etc/passwd")
+
+
+def test_validate_extra_info_path_rejects_dotdot_escape(tmp_path: Path) -> None:
+    with pytest.raises(ValueError, match="escapes"):
+        validate_extra_info_path(tmp_path, "../../etc/passwd")
+
+
+def test_copy_extra_info_skips_traversal(tmp_path: Path) -> None:
+    """A malicious extra_info path must not copy files from outside the task dir."""
+    secret = tmp_path / "secret.txt"
+    secret.write_text("top secret")
+    task_dir = tmp_path / "case"
+    task_dir.mkdir()
+    my_info = tmp_path / "my-info"
+    my_info.mkdir()
+    task = {"extra_info": [{"path": "../secret.txt"}]}
+    with pytest.raises(ValueError, match="escapes"):
+        copy_extra_info(task, task_dir, my_info)
+    assert not (my_info / "secret.txt").exists()
+
+
 def test_normalize_extra_info_accepts_legacy_and_schema_shapes() -> None:
     entries, warnings = normalize_extra_info(
         [