VM Network Traffic is visible to all VM in the same VLAN, but only if they are using VirtIO Network Bridge

Hello guys,

I am currently facing an Issue in our Proxmox Cluster as described in the Title.
It does not matter on which Node the VMs are on, or if they run Linux or Windows, it happens on every single one.
However LXCs in the same VLAN are not affected, since they dont use the VirtIO Adapter, as far as I can tell.

Here are some Infos on the current Setup:
Pakage Versions on each Node:

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