That's according to a Naruto fan site in Japan, known for posting spoilers. The site apparently received a message from a publisher, telling them to delete their articles and kindly asking them to shut down their site. Oh boy.
The site, called Naruto Channel with "Naruto Spoilers" in the URL, then deleted all plot point and character reveals. It then declared they were ceasing similar coverage in the future for both Naruto and One Piece. Both manga are published by Shueisha. This news comes from respected Japanese site IT Media (via Sankaku Complex).
Internet spoilers have supposedly hurt the Japanese manga industry, which previously ignored online spoilers. But, with sales on the slide, the industry is getting tough and, reportedly, starting to target popular spoiler sites like Naruto Channel, preferring to deal with the sites quietly.
However, IT Media's report states that "decisive action" will be taken against those who leak manga spoilers online. The industry reportedly won't just take action towards Japanese language spoilers, but English ones as well — anything that spoils or leaks info.
The report on IT Media isn't a hundred per cent concrete, and a lot of these leaks are hard to police. But for now, take this as a sign of things that might come.