BuzzFeed News became the center of a swirling debate over journalistic ethics on Tuesday after its decision to publish a 35-page document carrying explosive, but unverified, allegations about ties between the Russian government and President-elect Donald J. Trump.

The document, a dossier prepared by a former British intelligence officer hired by Mr. Trump’s political opponents, had been circulating among high-ranking politicians and some journalists since the fall. Intelligence officials recently presented a two-page summary of the allegations to Mr. Trump and President Obama, CNN reported on Tuesday.

But CNN declined to include the specific allegations contained in the dossier — such as collusion between Mr. Trump’s team and Russian operatives — saying that its journalists could not independently verify them.

Roughly an hour later, BuzzFeed, in a break from typical journalistic practice, posted the document that fully detailed the unverified allegations to which CNN had alluded.