[gh02t]

It might be possible if you find a hardware or software bug in the USB interface on the chip, but the Yubikey uses a chip designed specifically for security applications. Those sorts of chips are designed and tested explicitly for security applications are tested for all sorts of attacks and and exploits, both physical and in software. I doubt it's even physically possible to craft a USB packet that is able to interfere with the ADC on the chip enough to look like a touch event, but even if it was it'd be exceedingly difficult due to the nature of how USB signaling works. You don't have much direct control at the electrical level of what actually goes down the wire.