Hi there @Harvy!
Thanks for reaching out for clarification here in the Shopify Community.
Our developer team is aware of some cases where these preview links are incorrectly showing up in some stores' landing page sessions.
There is no security issue here, as these links are not made available to the public and are only showing visually internally.
You can filter these false positives out of the Sessions over time report by following these steps:
1) Go to Analytics then Reports
2) Click 'Sessions over time' within the Acquisition reports
3) Change the date range to 'Quarter to date' and hit 'Apply'. Group by day if this is not already selected.
4) Click 'Edit Columns' and add 'Landing page URL'
5) Click the 'Visitors' column to sort by number of visits. The '.shopifypreview.com' links gravitate towards the top number of visitors so they should show in the first 10 results.
6) Click 'Manage Filters' and set a filter for 'Landing Page URL' 'is not' and copy and paste in the '.shopifypreview.com' URLs and 'Apply Filters'.
This will filter out the incorrect info you have seen show up here and allow you to see more important data.
Thanks again for letting us know about this!