my half cents worth.
if bike was 100% b4 tucking to bed and it's only since it's been stood.
Most likely thing is if you washed it prior to putting it away and it has not been run immediatelly to dry out f/e around plugs and injector harnessesss and tps etc .
Most likely a damp joint gone maybbe green or just simply tracking accross.
My personall opinion is that pump controller might be culprit as the bowl in the tank fills with water expecially on gsa were controller sits.
Try spraying wd40 on plugs even better if you can blow them dry first .
Would second the comment on fuel been unlikely cause as takes years to go stale unless your unlucky enough to have topped up with shit b4 laying up.
Was told once that premium fuel can sepperate and causes varnishing in carbs on older bike had this with cbr600f. Alright to use but you must not let it stand.
Was advised to use straight unleaded if bike was layed up for long periods.
hope this helps.