* Oxymoron: A figure of speech that combines contradictory terms. For example, "living dead" or "deafening silence."
* Old News: The term refers to information that is no longer current or relevant. It is not contradictory, but rather a descriptor of the news's age.
While "old news" might not be the most exciting or captivating, it's a perfectly valid and understandable phrase.
Perhaps you were thinking of a different phrase, or maybe you're mistaking it for a synonym like "stale news," which could be considered an oxymoron.