nabucasa.com is a subscription service which provides secure access to users who run their own Home Assistant servers https://www.home-assistant.io/ for the purpose of remote access. The optional service supports the development of the free, open source project.
Each user receives a URL for accessing their Home Assistant instance which looks like "longrandomstring.ui.nabu.casa" with SSL certs provided by LetsEncrypt. There have not been any issues for many years but recently users who use both Malwarebytes and the NabuCasa service are having their URL blocked by the browser guard extension with a warning about riskware, and by mbam without notification.
I confirmed this using the Browser Guard extension and testing my own URL