SMS received blocked: xxxxx is your Facebook confirmation code.

Hello

First of all, I apologize to the moderators for not knowing which category to place this post in.
I didn't put it in [Internet/Facebook] because even though it is in the content, it has nothing to do with the subject of my question(s).

My problem:

While watching the new episodes of my favorite shows this Pentecost Sunday, I received a text message with the following:
xxxxx is your Facebook confirmation code

(I share it without fear, I know it's just phishing)
I do have an account on the social network but without using any Android application and was not logged in when I received the message, and above all, I do not share any data with Facebook (I even created a new email address to avoid disclosing my data to Zuckerberg's site) As for my name, it's a pseudonym.

Furthermore, I know that only I have access to my account, the American company spends enough money to ensure a minimum level of security for its users.

However, since I have a blacklist that allows me to stop receiving calls or messages from numbers I add to my smartphone, I wanted to add this one to it.
But here it is, it’s impossible the message is blocked, I cannot see its sender nor even reply. I can only read it or delete it

My question is where could this come from and how to avoid this type of inconvenience in the future?

(I should mention that I sell a lot on leboncoin, my number is therefore publicly available online, I think this must be where it came from, but usually it's not this sophisticated)

Thank you for reading my message, sorry for writing a lot, and thanks to those who will help me or share their experiences

To conclude, and because two precautions are better than one, I have still changed the passwords of my various accounts
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