[Mimedefang] Danger of .vcs files?

[Jim Hatfield]

I see that .vcs is listed in filter_bad_filename.

One of my users is subscribed to a mailing list and there
are often mails to the list with attachments called vcal.vcs.
Because we reject these at the gateway, the list management
software is getting tetchy and threatening to remove him
from the list.

If anyone can tell me what the danger of these files is,
I'd appreciate it, then I can decide whether to risk
letting them in.

jim