There are pictures of the phone, and of another phone with a similar symptom.

From the article:

So far, the finger of blame is being pointed at the battery. Unconfirmed reports state the iPhone 8 Plus uses the same battery manufacturer, Amperex Technology Limited (ATL), as the Samsung Galaxy Note 7.

But it’s worth remembering a couple of things. Firstly, many of the details surrounding this incident are hazy and unconfirmed. Take them with a grain of salt.

Exactly. If this is a widespread issue, we’ll see confirmed reports. If it’s a few flawed phones, this will quickly die off.