gh-160863: Restore tarfile data filter's resolved destination check

Lib/tarfile.py

@@ -895,6 +895,11 @@ def _get_filtered_attrs(member, dest_path, for_data=True):
         if member.islnk() or member.issym():
             if os.path.isabs(member.linkname):
                 raise AbsoluteLinkError(member)
+            # A link member that resolves to the destination directory itself
+            # would replace it with a (sym)link, redirecting the destination
+            # for all subsequent members.
+            if target_path == dest_path:
+                raise OutsideDestinationError(member, target_path)
             normalized = os.path.normpath(member.linkname)
             if normalized != member.linkname:
                 new_attrs['linkname'] = normalized

Lib/test/test_tarfile.py

@@ -4676,6 +4676,43 @@ def test_link_at_destination(self):
                     with self.check_context(arc.open(), filter):
                         self.expect_exception(tarfile.OutsideDestinationError)
 
+    @symlink_test
+    @os_helper.skip_unless_symlink
+    def test_link_resolving_to_destination(self):
+        # gh-160863: the 'data' filter rejects link members whose path
+        # resolves to the destination, even if the name is not lexically '.'.
+        def via_parent_name(arc):
+            arc.add('../dest', symlink_to='dest')
+
+        def via_symlink_to_dot(arc):
+            arc.add('d/')
+            arc.add('s', symlink_to='.')
+            arc.add('s/.', hardlink_to='d')
+
+        for make in via_parent_name, via_symlink_to_dot:
+            with ArchiveMaker() as arc:
+                make(arc)
+            with self.subTest(make.__name__):
+                with self.check_context(arc.open(), 'data'):
+                    self.expect_exception(tarfile.OutsideDestinationError)
+
+        # A symlink outside the destination that points at it must not be
+        # replaced.
+        with ArchiveMaker() as arc:
+            arc.add('first.txt', content='1')
+            arc.add('../current', symlink_to='real')
+            arc.add('later.txt', content='2')
+        with os_helper.temp_dir(self.outerdir):
+            real = self.outerdir / 'real'
+            current = self.outerdir / 'current'
+            real.mkdir()
+            current.symlink_to('real')
+            with arc.open() as tar:
+                with self.assertRaises(tarfile.OutsideDestinationError):
+                    tar.extractall(current, filter='data')
+            self.assertTrue(current.is_symlink())
+            self.assertEqual(os.listdir(real), ['first.txt'])
+
     @symlink_test
     @os_helper.skip_unless_symlink
     def test_empty_name_symlink_chain(self):

Misc/NEWS.d/next/Security/2026-10-29-13-00-00.gh-issue-160863.Kq7mVd.rst

@@ -0,0 +1,3 @@
+:func:`tarfile.data_filter` again rejects link members whose path resolves
+to the destination directory itself, such as ``../dest``.  :gh:`160097`
+had narrowed this check to names that are lexically ``.``.