any known security issues when opened email on iphone that automatically downloaded H E I C file

Hi. I normally don't click on emails from people I don't know. Yet, I clicked on an email on my iphone and it automatically downloaded the attachment for viewing. The attachment was a H E I C file. I was surprised as I didn't expect it to automatically open the file. The email was a scammer/phisher. Has anyone else experienced this before? Is this a new or known security exploit? Any advice?

This support Apple page doesn't mention this use case.

Recognize and avoid social engineering schemes including phishing messages, phony support calls, and other scams - Apple Support

Any insight would be much appreciated. Thank you!