This is a variant of what I call "copy/paste" spam, where the spam post is a copy of existing legitimate content, with a spam payload inserted.
This type of spam can be especially harmful because it appears to be a legitimate post, causing the helpers here on the forum to waste their time responding.
In this case, they assembled the content from previous posts in the same forum topic:
The spam payload was hidden in the - character in the URL (the goal is typically to get SEO for the site through backlinks, rather than getting people to actually click the link directly).
The source markup of the post looks like this:
I should add that you won't be able to see the icons in my last reply if you have the forum configured in the light mode because of the white background. but I think you can turn it off and try these types of websites: https://github.com/arduino/arduino-create[-](https://bit.ly/394UY2L)agent/pull/575
(Note the - was linked to a bit.ly URL).
You can see the source markup of any post by selecting the text and then selecting "Quote" from the menu that appears. The source will then be added to the post composer window (wrapped in [quote] tags). Obviously, there is no need to actually post the quote, just look at the source in the post composer window before deleting it.