A post from the Italian website HTNovo states that Microsoft added 11 CCleaner domains to a blacklist in official Answers support site.
It is quite common to see forums blocking specific sites, e.g. sites that are malicious in nature or problematic for other reasons. But it is very rare for legitimate websites to be blocked in official forums of large companies.
The Italian website reveals that the domain www.cleaner.com is one of the domains blocked by the company but does not mention the other ten that Microsoft added to its blacklist. The image above shows the URL of a hidden forum (moderators forum) that lists all blocked domains. Last you will see ccleaner.com.
A quick test in the Microsoft Answers forum confirms that the ccleaner.com domain automatically changes to **** when included in a post. It doesn't matter if the protocol is used or www, the domain changes automatically after publication.
Why did Microsoft exclude this domain? No one can say for sure.
But let's remember the course of application: