I found weird email address appended to some of my URLs, what does that mean?

I have a wordpress site, i foundout that there are some urls have an email address appended to them. examples: https://www.mydomain/page-slug/admin@education-lms.com this url return 404 not found. the domain "education-lms.com" is not returning anything when you search for it.

When performed a databse search, I found 7 cells in wp-options table conain the text "admin@education-lms.com" although that email was never used at all for the website.
I have removed the email from my databse table, but my question is; do i need to worry about that? especially i had some work done on the site by a developer on Upwork. or I should’t worry about it as long as i removed it?

By the way, it is not on all pages/posts, only some of them.

Please help. Thanks