the word 過ぎる（すぎる） literally means "to go over/to surpass." So, when paired with a verb or adjective, it expresses an excess of something. In English, we would say "too cute" in this case. Usually, the use of すぎる expresses a negative quality, but in this context it is positive, because it is simply emphasizing how cute something is. Some other examples of すぎる 高すぎる - too expensive やり過ぎる - to do too much 読み過ぎる - to read too much 早すぎる - too early 長すぎる - too long I hope this explanation is clear. Please let me know if you need further explanation.

Also we usually say このりんごおいしすぎる（うますぎる）＝the apple is really good 楽しすぎる＝really fun おもしろすぎる＝really funny like that☆

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