Learn Italian: Abbiamo trovato qualcosa di strano, forse un bug. - We found something strange, maybe a bug.

When you describe an indefinite pronoun like qualcosa (something) or niente (nothing) with an adjective, Italian requires the preposition di between them. You cannot just translate literally and say qualcosa strano.

Does the adjective strano change depending on what we are talking about?

No, an adjective that follows qualcosa di always stays in the default masculine singular form. Even if the 'something' refers to a feminine object, it remains qualcosa di strano.

Why does the English word bug take the masculine article un?

Italian adopts many English words, especially for technology and the internet. As a general rule, foreign loanwords are treated as masculine by default unless they refer to a specifically feminine concept, and they do not change form in the plural.

Could I say qualche cosa instead of qualcosa?

Yes, qualcosa is just a combined, shortened form of qualche cosa. They mean the exact same thing and are used the same way. If you use the full version, you still need the preposition before the adjective: qualche cosa di strano.