BEIRUT, Lebanon — To the overnight editor at the Arab affairs website, it looked like big news: Kuwait, apparently following the lead of President Trump, had issued a visa ban on citizens from five other predominantly Muslim countries.



The editor wrote an article, and the news rocketed through cyberspace. One link caught the eye of Mr. Trump himself, who shared it on his official Facebook page with a word of praise for the reported policy: “Smart!”

But there was a problem: The Kuwait ban was from 2011, long before Mr. Trump announced a similar measure in the United States, said James Brownsell, the managing editor of The New Arab, the site that produced that article on Feb. 1. His writer did not notice that the news was years old.

Many sites that often support Mr. Trump and also published the report, including Infowars.com and Russia’s Sputnik news agency, have since clarified that it was outdated and unrelated to Mr. Trump’s order.