Yes. Some older flashes use much higher trigger voltages than modern electronic cameras expect, and that can damage the camera’s hot shoe circuitry.

The key spec is the flash’s trigger voltage. If you can’t find it in a reliable trigger-voltage chart, you can measure it. The exact Metz 18 B1 wasn’t identified in the answers, but a related Metz 20 B3 was reported around 168V, which shows that older Metz units can be high-voltage designs.

Based on the community answers, the Canon 7D is reported to tolerate up to about 250V, so your flash may be safe with that specific camera even if it has relatively high trigger voltage. Still, it’s best to verify rather than assume.

If you want extra protection, use a hot-shoe safe-sync/high-voltage regulator. That isolates the camera from the flash and is the safest on-camera option. Another possibility is using the flash off-camera with a remote trigger, but you’d still need to confirm the trigger can safely handle the flash voltage.

So: yes, the risk is real with some old flashes; check or measure the trigger voltage, and if in doubt, use a safe-sync adapter.