System1 is trading 5.45% higher at $2.90 in after-hours trading after a sharp reversal following several down sessions; no confirmed company-specific catalyst was identified. - The stock closed at $2.75 on September 28, 2026. - System1’s investor-relations news page lists 2026 news, but the retrieved listing showed no September 28 announcement. - Broader markets were lower amid oil-price and rate concerns, which do not clearly explain the after-hours move.