Not knowing your location from your Profile, this might be a St. Andrew's Cross. Non-toxic and catches many bugs.
Did you happen to count how many eyes? Does it hang inverted on its web? Does the web have the jagged "cross" pictured below?
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This is in Goa India, and yes he / she was hanging upside down. Didn't notice the thicker cross web. Definitely didn't go close enough to check the number of eyes : )
Is your "surprise" based on knowledge? Or fantasy?
Of 34,000 spider species, about 12 have venom harmful to humans...that's 0.035%
You have a greater chance of a train injury in Mumbai ;)