The missile that hit Poland yesterday was likely a Ukrainian air defense missile intending to intercept Russian missiles during yesterday's bombardment.
Prior reports suggested the missile was Russian-made, and some of the Ukrainian air defense systems like the S-300 are former Soviet missile systems.
Poland has withdrawn its Article 4 request.
Of course Russia is blaming this on Ukraine and saying it didn't fire on Kyiv yesterday, even though the entire reason for the air defense systems are the Russian missile strikes...