Officials sent two warnings to Washington about the lab. The column says the officials were worried about safety and management weaknesses at the Wuhan Institute of Virology (WIV) and called for more help." ... "What kinds of security failures were the cables describing?
The short answer is we don't know from the information provided in the Washington Post. But, generally speaking, there are multiple ways that safety measures can be breached at labs dealing with biological agents.
According to Dr Lentzos, these include: "Who has access to the lab, the training and refresher-training of scientists and technicians, procedures for record-keeping, signage, inventory lists of pathogens, accident notification practices, emergency procedures.""
In other words, all the information is non-public and coming from the entirely unreliable US Intelligence services whose job is to lie and make the US government look good. If these reports had been published (meaning in public documents) prior to the pandemic OR there was an admission by the Chinese government, this would be far more credible.