hello, if you're using and addon like ublock it will have the option to download various filterlists, among them one from the domain you've mentioned in order to block malicious sites.

Thanks a lot for replying. You are right, it was related to the Ublock Origin plugin. But after I allowed it to connect to malewaredomainlist.com to update the filterlist I get more alerts for the following domains:

pgl.yoyo.org oscp.int-x3.letsencrypt.org ocsp.int-x3.letsencrypt.org.edgesuite.net

Am I safe to let them too connect to the Net?

pgl.yoyo.org is hosting a list of adservers, so i suspect it's just another provider of filter lists you've configured in ublock.

ocsp is a protocol to verify with the vendor of a certificate that it is still valid and unrevoked when loading a secure site via https, so probably best to allow those connections too...

Let's Encrypt is a legitimate SSL certificate authority. More info: https://letsencrypt.org/about/