Update (9:35 a.m.): Updated with Wednesday market open information.
The stock was down 18.65% to $30.20 at 9:35 a.m. on Wednesday.
Mondelez could see a big hit in sales.
The ransomware strain disrupted Ukraine, but has not provided its creators with much cash.
Tuesday's high-profile attack and last month's WannaCry attack could boost cybersecurity spending, but the bump might already be priced into the stocks.