Ran out of fermenter space..Help!

I was making a 7 gal batch of foreign extra stout and ended up with 8 gal of wort. I scrounged around and found a large wine bottle with a screw cap. I drilled a hole to insert a airlock and used plumbers tape to get a better seal. I am still very early in fermentation but all vessels except the rigged one are bubbling fine. I see no bubbles in the air lock but signs of fermentation in the bottle. I am obviously not sealed. My question is if when I take a gravity reading and it has in fact had a active ferment am I safe to think that the fermentation has kept any nasty`s out?

Yeah, usually. I've had to fashion various blow-off tubes that didn't fit perfectly*, and still had no issues.

*Note: by perfectly I mean like, 1/8 of an inch gap. So I'm sure you're fine. Just keep it clean.*

Cool, That's what I was hoping to hear. Thank you