This question is meant to ask for general guidance - although I will mention a specific example. (It is not my intention to call out a specific user - simply the issue is better explained on an example.)

I have noticed a domain which has several links on Stack Exchange ([28 posts](https://stackoverflow.com/search?tab=active&q=url%3a%22%2Abillthelizard.com%2A%22) on Stack Overflow and [34 links](https://stackexchange.com/search?q=url%3a%22%2Abillthelizard.com%2A%22&pagesize=50) networkwide.) 
When trying some of those links I got the warning:

> Threat found
> This web page may contain dangerous content that can provide remote access to an infected device, leak sensitive data from the device or harm the targeted device.
> Threat: JS/Redirector.PSC

It seems likely that the domain worked in the past. (I managed to find Wayback Machine links for some of those posts.) But after the domain expired, somebody else used the same domain and placed some harmful content there

What should be done in situations like this?

 * Should I try to replace the links by the Wayback Machine links, if they are available?
 * What should be done 
 * If some site has many such links, should I notify the mods? Should I mention this on the per-site-meta?
 
In this case I have option to notify the owner of the domain - the user seems to be still active on Stack Overflow. But in other similar cases, there might be no such possibility.