Will my offer be rescinded for what I want to try?

Recently accepted a tier 2 bank summer analyst role in NYC in Lev Fin.

I am meant to be going for my masters this year to break into IBD as I have full time work experience and I was told by the MD in the final interview they usually don't take people with FT experience for SAs but they'll take a limb out on me since I interviewed so well.

That's all good and dandy but I have now seen a FT experienced position that is looking for someone with my exact profile (they want someone that has interned in Lev Fin and has the same FT experience I have) at a big 3 BB in also in NYC.

I want to apply and if I get the job start right after I finish my lined up SA stint and leave the masters. (I really don't want to do a masters I would rather start as an analyst this year than wait till next year if I even get a return offer).

My fear is the hiring manager or someone at the team in the BB would contact the company I currently have lined up and tell them I plan on ditching the masters which was a major reason they gave me the job in the first place. I understand banking is cut throat and there is a lot of backstabbing and shitty people so this is a major fear of mine as banking would literally change my life and those of my family. 

What do you guys think about this, am I over thinking?. Even if my current firm finds out would they actually rescind my offer?  Is there a possibility of someone snitching? I am also considering emailing someone on the team rather than through the portal to make things more harder to trace.