How to "safely" add external links to the site?

Question

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About six months ago, this happened on my site.
Only on the page for setting a new password (which the user accesses via the password reset link from the mail), the following warning began to appear in chrome:

Attention! Perhaps this site was created for the purpose of phishing!
The website contains elements from other sites that we know to be phishing. Phishing sites trick users into obtaining personal or financial information by impersonating trusted institutions such as banks.

The site is typical and in its footer there were icons / links to various social networks, including the VKontakte group. I found out that it was the link to the VKontakte group. Without it, the phishing message did not appear.
As a result, I decided to remove the block from the social. links from all pages somehow related to account management.
This safebrowsing.clients.google.com/safebrowsing/diagn...
service at that time reported that "This site is not currently listed as suspicious.". Both for the url to the group, and for just the main VKontakte.
I assume that this happened with just one page because:
1) a link to a "phishing" site, in this case VKontakte
2) a link to the page was received via mail
3) on the page itself, a form with fields for passwords
. A couple of questions:
1) If my conclusions are not correct, why exactly could this happen?
2) And is it possible to somehow avoid this in the future without removing the links?