Me to a major vendor, in a PGP-encrypted email (their request):
Describes vul in their software. Here's an animated GIF showing exploitation of the vul. Please let me know how I can get a large file to you so I can get the PoC to you.
Vendor (in cleartext): Please send us a GIF and the PoC.
Me: I already sent the GIF. Are you saying you didn't get it? Also, please tell me how to get a large file to you.
Vendor: We have not received the GIF. Please send us a PoC.
Me: table_fip.gif
I fully understand why people go the full disclosure route.