Deployment of a V2 function fails with [error]Error: Malicious entry: bin\extensions.json

We are experiencing issues when running Azure DevOps Release pipelines to a v2 azure function (netcoreapp2.1). The function has a trigger reading from a ServiceBus:
[ServiceBusTrigger(Topic, Subscription, Connection = "ConnectionString")]string messageBody,

We get the following errormessage when trying to run the Release pipeline:
Errormessage: [error]Error: Malicious entry: bin\extensions.json

2019-04-04T14:32:40.6434473Z ##[section]Starting: Azure Function App Deploy: eventfeeder-dev-rettsdata
2019-04-04T14:32:40.6531661Z ==============================================================================
2019-04-04T14:32:40.6531768Z Task : Azure Function
2019-04-04T14:32:40.6531872Z Description : Update Azure Function on Windows, Function on Linux with built-in images, ASP.NET, .NET Core, PHP, Python or Node.js based Web applications
2019-04-04T14:32:40.6531975Z Version : 1.0.4
2019-04-04T14:32:40.6532036Z Author : Microsoft Corporation
2019-04-04T14:32:40.6532261Z Help : [More information](https://aka.ms/azurefunctiondeployreadme)
2019-04-04T14:32:40.6532349Z ==============================================================================
2019-04-04T14:32:41.2679166Z Got service connection details for Azure App Service:'eventfeeder-dev-rettsdata'
2019-04-04T14:32:41.5318495Z ##[error]Error: Malicious entry: bin\extensions.json

....

extensions.json is included in the build artifacts (in the /bin folder)

When running a build that was successful from 2019-03-26, it fails with the same errormessage.

I even tried to recreate the function.

The content of extensions.json:

{
"extensions":[
{ "name": "ServiceBus", "typeName":"Microsoft.Azure.WebJobs.ServiceBus.ServiceBusWebJobsStartup, Microsoft.Azure.WebJobs.ServiceBus, Version=3.0.3.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"}
]
}