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LOS ANGELES — Financial data and news service Bloomberg moved to repair damage to its reputation Monday as a published report said that more than 10,000 of its clients’ private messages containing sensitive pricing data had been leaked online.

The report came the same day Bloomberg News editor-in-chief Matthew Winkler apologized for the news service’s practice of allowing journalists to access data about how clients used the company’s financial-data services.

Reporters have had access to the data, Winkler said, since the 1990s but it was revoked last month after investment bank Goldman Sachs complained.

Bloomberg’s data services provide financial-market information and news, an instant-messaging program and trading platforms to users. The services, which are mainly accessed by way of the company’s proprietary computer terminals, are widely used in the financial industry and beyond. More than 315,000 clients pay roughly $20,000 per year for the right to use them.

The mishaps involving Bloomberg’s handling of what traders had thought was private information were seen as damaging, but not insurmountable for the news juggernaut founded by New York City Mayor Michael Bloomberg in 1981.

Regarding the leak, The Financial Times said Monday that messages between traders at dozens of large banks from one day in 2009 and one in 2010 had been put online by a former Bloomberg employee.

The Financial Times said it was possible the employee intended them to be uploaded to a secure site. A Bloomberg spokesperson told the newspaper the post was a “clear violation of our policies,” and added that it was considering legal action on the matter.

Earlier Monday, Winkler apologized in an online post.

He explained that journalists at Bloomberg News, until recently, had been able to see when clients last accessed their Bloomberg terminals. They were also able to view broad categories of functions that clients used, such as one that looks up credit ratings.

Goldman Sachs had complained to Bloomberg management about the practice after a Bloomberg reporter told the company that she had used login data as a clue in her investigation into whether a Goldman employee had departed.

“Our reporters should not have access to any data considered proprietary,” Winkler said. “I am sorry they did. The error is inexcusable.’’