News leak

A news leak is the unsanctioned release of confidential information to news media. It can also be the premature publication of information by a news outlet, of information that it has agreed not to release before a specified time, in violation of a news embargo.
Types.
Leaks are often made by employees of an organization who happened to have access to interesting information but who are not officially authorized to disclose it to the press. They may believe that doing so is in the public interest due to the need for speedy publication, because it otherwise would not have been able to be made public, or to rally opinion to their side of an internal debate. This type of leak is common; as former White House advisor Sidney Souers advised a young scholar in 1957, "there are no leaks in Washington, only plants."
On the other hand, leaks can sometimes be made simply as self-promotion, to elevate the leaker as a person of importance. Leaks can be intentional or unintentional. A leaker may be doing the journalist a personal favor (possibly in exchange for future cooperation), or simply wishes to disseminate secret information in order to affect the news. The latter type of leak is often made anonymously.
Sometimes partial information is released to the media off the record in advance of a press release to "prepare" the press or the public for the official announcement. This may also be intended to allow journalists more time to prepare more extensive coverage, which can then be published immediately after the official release. This technique is designed to maximize the impact of the announcement. It might be considered an element of political 'spin', or news management.
Some people who leak information to the media are seeking to manipulate coverage. Cloaking information in secrecy may make it seem more valuable to journalists, and anonymity reduces the ability of others to cross-check or discredit the information.
Some leaks are made in the open; for example, politicians who (whether inadvertently or otherwise) disclose classified or confidential information while speaking to the press.
Leaks can have strong consequences. President Richard M. Nixon was enraged by the existence of leaks, and according to his former staffer William Safire, that rage coupled with the president's lifelong disdain of the press set the environment that led to Nixon's downfall. Most immediately, fear of further leaks after the Pentagon Papers were published in 1971, such as of the Secret Bombing of Cambodia, led to the formation of the "White House Plumbers" unit (so named because they wanted to fix leaks), which conducted the break-in that led to the Watergate scandal and Nixon's eventual resignation in 1974.
Reasons.
There are many reasons why information might be leaked. Some of these include: