Firewall blocking LoL client?

So I just logged in the LoL client (not even the first time this patch) and I have my firewall pop up and say it blocked the LoL client. I allowed access because I know LoL is safe but I'm just wondering, why did it happen? never happened to me before. (This is the exact route: C:\riot games\league of legends\rads\projects\league_client\releases\\deploy\leagueclient.exe)
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