Virus

Hello,

Don't worry, this is not a virus but rather you might have allowed and access for a website to create reminder on your calendar and iPhone would always ask you before it happens, follow this;

Settings > Calendar > Accounts > Choose an event account being fed from website link > Erase account

You can also learn more via how to ''Remove spam from Calendar on your iPhone" https://support.apple.com/en-us/HT211076

Have a great day!

We are very happy to now that it worked. Don't worry just be mindful before visiting potentially unsafe websites.

Some websites might pop up unsafe links and advertisements and some are might ask you to allow an access to calendar but this will never infect your running iOS software.

The best way to prevent these issues will start with Safari.

On your iPhone, iPad, or iPod touch, go to Settings > Safari and turn on Block Pop-ups and Fraudulent Website Warning.

I found this, I hope it's useful for you

About pop-up ads and windows in Safari

https://support.apple.com/en-us/HT203987

If running iOS 13 or earlier versions, check: Settings - Passwords & Accounts - Accounts - Any rogue entries here? If so, delete the rogue account. 

If running iOS 14, check: Settings - Calendar - Accounts - Any rogue entries here? If so, delete the rogue account. 

Tap on Subscribed Calendars. You should find a calendar that doesn't belong there and is generating all of the fake messages. Delete it.

Tap the one that says “Subscribed Calendars”. The bogus calendar should be hiding there.