TL;DR: What the title says. The below text is just how I got to this possible bug.
I have just started playing KSP and thought the deployable experiments may be fun to do, so I went and did it, the destination was Mun. Being new to KSP and half asleep, I then forgot to extend an ladder all the way down to the ground. And since to deploy the deployable experiments, you needed the item in the inventory of your Kerbal, which has limited space, I had to clear the inventory of the Kerbal, including the EVA-Jetpack. When I realised that my command module was too far away from the ground for me to reach, and I had no ladder, I decided to jump next to my rocket, so I had a brief momnet where I could transfer my items into the inventory of my Kerbal.
It went well once, but the next time I only got the item from my command capsule and forgot to open the inventory of my Kerbal. When the Kerbal landed on the ground, I proceeded to open the inventory and, since I still had the item selected with my mouse, put the power module into the inventory of my Kerbal. This is where things started to get wonky. Because the Kerbal was out of range of the command module, the item couldn't possibly have been transfered to my Kerbal, but I clearly still had the module on my mouse. So the power module decided to just... stay on my mouse, presumably until eternity. I was really sleepy and just wanted to do this one thing right, so I went for a refresh, meaning going to the KSC and then back, which resulted in the power module staying on the blue button leading to the KSC.
That was acceptable for me, because it didn't really affect gameplay anymore, instead it was just a small icon on the top of my screen. And I had a quicksave before I landed, so I just used that one. After I landed I happily found out that all modules are still in my command capsule, so I deployed them one by one (without screwing up again), which went well, until I went inside the command capsule. There I found out that my Kerbal still had a power module in her inventory. Which was nice for me, since I had no engineer, so I needed two of the power modules, which I have previously forgotten. So I thought maybe I had planned to take two power modules all along, and deployed that power module once again. But when I went inside the command capsule, the power module was in the inventory of my Kerbal once again. My sleepy mind finally kinda woke up, becoming suspicious, and placed that module again, and again, and again... you get the point.
What I am saying is that my deployable power module got replicated infinitely. Sorry for talking so long just to reach this point, but this bug seemed to be very specific for me, so I wanted to be as detailed as possible. Unfortunately I have not made any screenshots, as I kinda forgot that there was a forum. I might try to replicate this bug again and take a few screenshots when I am less busy, though. For now I hope this much information is sufficient.
