The couple saw brushes and paint cans in front of a paint-splattered canvas at a gallery in a Seoul shopping mall. So they added a few brush strokes, assuming it was a participatory mural.

Not quite: The painting was a finished work by an American artist whose abstract aesthetic riffs on street art. The piece is worth more than $400,000, according to the organizers of the exhibition that featured the painting.

Now it’s hard to tell where the artist’s work ends and the vandalism begins. “Graffitied graffiti,” a local newspaper headline said last week.

Either way, the piece, “Untitled,” by John Andrew Perello, the graffiti artist known as JonOne, is now a magnet for selfies. And on social media, South Koreans are debating what the vandalism illustrates about art, authorship and authenticity.

The artwork is displayed with paint cans, brushes and shoes that the artist used when he worked on it, one of the exhibition’s organizers, Kang Wook, said in an interview. He added, “There were guidelines and a notice, but the couple did not pay attention.”

Some social media users have echoed Kang’s reasoning. Others say the sign was confusing and the couple should not be blamed.

A few suggest that the incident itself was a form of contemporary art, or that the couple’s abstract brush strokes — three dark-green blotches covering an area about 35 inches by 11 inches — have improved the piece.

The debate is notable in part because the crime was not intentional and the painting can be restored, said Ken Kim, an art restoration expert in Seoul who has seen the vandalized work.

The painting is part of “Street Noise,” an exhibition that opened at Lotte World Mall in Seoul in February and features about 130 artworks by an international group of more than a dozen graffiti artists. Kang said the staff at the mall noticed March 28 that the painting had been vandalized and identified the couple by checking security footage.

The couple were arrested but released after police determined that the vandalism was accidental, the local news media reported. Kang said the couple told the police that they had thought the artwork was open to public participation.

VR Sunil Gohil