The Argentina star's reflection was spotted by fans as the snap went viral.
Musso unwittingly exposed himself in a thank you post to Italian girlfriend Anna Ariaudo after returning from international duty to find their home filled with red helium-filled balloons and ‘I Love You’ written on them.
The 27-year-old wrote ‘You’re the best’ alongside his initial post - which bared all of him from the tops of his thighs to the mobile he was holding up in front of his head.
But he took the gaffe in good spirits as he replaced it after he realised his blunder with a photo showing him clothed alongside the words: “The correct photo. Morning @annaariuado" - followed by laughter emoticons.
His girlfriend responded with the same snap and her own emoticon showing a woman with her hand over her face to express embarrassment under a message which said: “Luckily I love you too much.”
Musso was on the receiving end of strings of memes as his original photo did the rounds.
One showed Manchester City legend Sergio Aguero interrupting a video game to stare at his phone with a look of disbelief on his face.
Musso, 27, was signed by Udinese from Argentina’s Racing Club in the summer of 2018.
He quickly established himself as the undisputed starter and was signed by high-flying Serie A rivals Atalanta last July.
He made his debut for the Argentina national team on March 26 2019 in a friendly against Morocco.
He played the 90 minutes in Argentina’s 3-0 World Cup qualifier victory over Bolivia in September.
Chelsea reportedly set their sights on Musso in March 2020 as a replacement for Kepa Arrizabalaga when the Spaniard’s form was being questioned.
He played in goal for Atalanta in October when Cristiano Ronaldo headed the winner nine minutes from time as Manchester United came from two goals down for a memorable Champions League triumph at Old Trafford.