The pitch invader made a beeline for Ronaldo and reached the striker, who was facing the opposite direction and did not see the fan approaching.
Ronaldo managed to evade the supporter before showing his disgust, with the fan eventually being led away by security.
As Ronaldo chatted with team-mate Miralem Pjanic, the fan came up behind the five-time Ballon d'Or victor with a mobile phone and tried to put his arm around the Portugal star's neck. Unfortunately for the fan, he did not get a pleasant reaction from the superstar.More news: Acid attack survivor Katie Piper is all praise for Deepika Padukone's Chhapaak
Peter Bosz's side had the best of the chances in the first half but Ronaldo tapped home from Paulo Dybala's cross in the 75th minute and Higuain drilled into the bottom-right corner in stoppage time to send the hosts into the Europa League.
Juventus have certified for the Champions League Spherical of 16, topping their group.
With the 2-0 win Wednesday, Maurizio Sarri's team finished as Group D leaders, which meant they'll be seeded in the Round of 16 stage.
It was Ronaldo's third goal in as many games and his ninth of the season.More news: Jackson Alexa voice arrives: Here’s how to use it
"I feel good, the physical problems I had have passed", he said. "I have more confidence and hope to continue like this".
Juventus veteran Gigi Buffon has warned his young teammates not to take playing in the Champions League for granted.More news: European Union claims success on flagship climate change policy - but Poland says no