Please pardon my somewhat peculiar case, I hope this is still a question useful to others.
After school I became an undergrad but paused studying after a few semesters of university to work full time. During the several years I was employed, I also became co-author of three papers, two of which were were with a "potential, possible, or probable predatory scholarly open-access publisher".
At the time I was not aware journals like that even existed, and as a professor and two doctors were also authors, I would never have imagined this could be an issue. As I am now a university student again and learned about this, I obviously regret my decision to participate. I am not sure how my mistake will be judged by others, and how far-reaching the consequences are, this is why I am asking here.
To be honest, I think it, while bad, was no terrible blunder, as I was "only" an employee at the time (though an undergrad before that). Also, I suspect most future employers would probably not even recognize my mistake.
Clearly it is different if I were to pursue an academic career. Are past flaws of this kind forgivable - and if so, should I (actively) point out that I made a mistake and will avoid it in the future?
Annotation: Many people claimed (elsewhere) that the journal in question did no peer-review. This was not the case for me, as we always had a list of (content) issues to address, usually by 4 to 6 reviewers.