# Test Case: Truncated metabox super extension

**Test ID**: TC136-metabox-truncated-super-extension
**Fixtures**: `bad-metabox-truncated-extension.erofs`, `bad-ishare-prefix-id.erofs`

## Objective

Reject `METABOX` when `sb_extslots=0` leaves `metabox_nid` undeclared, and
reject `ISHARE_XATTRS` when its prefix ID equals `xattr_prefix_count`.

## Manual steps

For each image, attach it and trace the read-only mount:

```sh
truss -f -o /tmp/tc136.truss mount -t erofs -o ro \
  /dev/${unit} /mnt/repo22-g4
grep nmount /tmp/tc136.truss
mount | grep repo22-g4 || true
mdconfig -d -u "${unit#md}"
```

## Expected results

Both `nmount` calls return `EINTEGRITY` (97). The extension bytes are not
consumed, no mount appears, and detach succeeds without a vnode/md leak.