Workflow published on List A runs on items in List B
A workflow published on List A will run on items created in List B as well.
In List B, navigate to List Settings > Workflow Settings > Remove, Block, or Restore a Workflow > Select "No New Instances"
Note: If you select "Remove", the problem will continue occurring and the workflow will not appear in the Workflow Settings.
This tends to occur when a List Template is created from a list that has a workflow published on it. The most common occurrence of this is when the workflow on List A is configured to initiate on Item Creation prior to creating the List Template, therefore, the workflow also initiates on Item Creation that occurs in List B and any subsequent list created from this List Template.
This is a behavior in SharePoint and can be replicated with SharePoint Designer Workflows.