There is a blank character (kind of box) that can be used in WhatsApp to set blank status or send blank messages.
How to create/type or find that character?
The methods shared here unfortunately do not work; the Arabic Character used to work but it stopped working since long. The only character which seemed to work was the Reverse Character Unicode [which I discovered in 2005] Pasting or Opening it on a PC messes it up. Afterwards I stumbled on another unicode character which would work (on most devices) even when shared through PC etc.
Copy the Space visible between the bold brackets [ ] .
If for some reason you fail to copy it from above you may copy it from my blog > here.
The box type thing you mentioned appears on Apple devices and the proper technique wouldn't result in a box type thing even on Apple devices.
Fun Fact : I was the one who worked out the "blank character" thing on the internet more thn 2 yrs back and finding others using(stealing) even "my images" spoils the mood, thus I came here to post the same.
Just go to your computer, go to character map (or a word document) and hit ALT + 255 or ALT + 0160 and copy that file into your phone. Then open that document on your phone, copy the text and paste it wherever you want.
However, if you don't want to waste time doing all this; just go to your WhatsApp settings and hide your status.