The hackers published the file containing the keywords coded into a web forum Russia.
They invited the hacker community to help solve the key word.
LinkedIn, which has more than 150 million users, said the key word has leaked that no longer applies.
Users will receive an e-mail with instructions to change it, said LinkedIn. They will receive a second e-mail with details on why the change was necessary.
Concerns about privacy
The news comes as the LinkedIn applications are forced to update their cell phone after security researchers discovered a flaw privacy.
Skycure Security said that the phone app sends calendar data without the password to the server LinkedIn "without the knowledge of" users.
That information includes meeting notes, which often contain information such as phone numbers and key codes for conference calls.
LinkedIn answer the, the application it does not anymore send data from sexy a memorandum of meeting your calendar.
The company also stressed that the calendar function is a feature option.
However, the researchers who discovered the flaw, said transmission data to the server LinkedIn performed without a "clear indication of the application to the user".
In a statement published on the company blog, the Head of Mobile Product LinkedIn Jeff Redfern said more information was added to the application so that users get a clearer picture of the transmission and use of their information.