Is Dove's Trojan horse illegal and if not, why not?

Assuming this article is actually true Dove Canada Uses Photoshop Trojan Horse to Shame Potential Body-Shamers , isn't this a variation of an 'unauthorized action' against a user's computer?

For example here in the UK,  couldn't this be used on an CMA (Computer Misuse Act) case?

After all, Dove knew they were doing an unauthorized action, and Dove is profiting from it.

My view is that the CMA (and similar laws) are completed crazy and make any Internet user a (potential) criminal. So with that in mind, what is the deal with this Dove trojan horse? Is that legal?

Here is a reddit thread about this article, that doesn't mention the legal side of things: Not a IFF post, but an excellent message from Dove about body image and Photoshop.