Upload an image to copilot new conversation but no command, the response will basedthe context of a historical conversation.

Looks it's a bug.
I upload an empty black image, copilot response me the content about "Subnet Mask", it's one of the earlier conversations.

The other test. This is a solid-color image captured from the Copilot webpage. Copilot response me "I (copilot) have no April Fools' Day Easter eggs" — it's also the one of previous conversations. Tried attempt, the image contains text, copilot response me "Easter eggs" topic again.
But interesting, this time it seems to have detected that I upload an image — and assumed I was attempting to embed text like "Debug:true" within a "greeting image" — the actual text in image was "Hello Flithor,", it's captured from the Copilot webpage too.

It seems to have understood the content of the image, but since this is a "new conversation," it has conflated memory context with the new conversation.