CBS News claims that several criminal investigations involving State Department employees, including at least one ambassador, were covered up or ignored in order to avoid embarrassing the diplomatic service. According to a memo written by the department's Inspector General's office, several members of the Diplomatic Security Service, which is in charge of protecting American diplomats overseas, were told to back off or stop investigating some of the cases, ensuring that no charges were ever brought.
Among the alleged crimes that were covered up: Reports of a "drug ring" near the U.S. embassy in Baghdad, claims about a State employee in Beirut sexually assaulting foreign nationals, and agents on security details (including some who were protecting former Secretary of State Hillary Clinton) soliciting prostitues while on official trips. It's also likely that foreign (and "hostile") intelligence agencies were aware of the behavior.
In the most shocking incident, a U.S. ambassador in a "sensitive deployment" was believed to be eluding his own security detail so that he could "solicit sexual favors from prostitutes" in a public park. According to CBS's well sourced John Miller, despite being recalled to Washington for scolding from his bosses, that person is still the ambassador.
It is worth noting that in all of these cases, no charges were ever brought forward and all the allegations might have all turned out to be nothing. However, no one knows for sure because the investigations were shut down before they could be completed. It's also not the kind of story the State Department (or the Obama administration) needs after nine months of questions about their handling of Benghazi, a similar scandal involving the Secret Service, and the whole "non-stop spying on everyone in America" thing.
The memo was drafted as part of Inspector General's report on the DSS, and originally contained eight specific references to criminal allegations. The final report was scrubbed of all references.
Miller's CBS News report also doesn't say who could have influenced or shut down such investigations, but one former investigator who said he was told to stop an investigation claims it had to have come "from somebody higher than (Diplomatic Security)." Another former agent, who is now considered a whistleblower for trying to bring the report's attention to Congress, says that with two hours of CBS News contacting the State Department for a response, IG investigators showed up at her house to ask questions.