Magento released security patch SUPEE-10570 on Feb 27th 2018 and SUPEE-10570v2 on April 3rd 2018. We monitored the impact on OneStepCheckout and found an issue with SUPEE-10570v1. Here are the details of the issue as well as the fix. Read more »
Magento SUPEE-10570 Security patch: impact on your checkout and fix