A former security chief for Twitter has turned whistleblower and testified that the company misled users and US regulators about gaps in its security.
Peiter Zatko also claimed that Twitter underestimated how many fake and spam accounts are on its platform.
The accusations could affect a legal battle between Twitter and billionaire Elon Musk, who is trying to cancel his $44bn (£37bn) deal to buy the company.
Twitter says Mr Zatko's allegations are inaccurate and inconsistent.
It says he was sacked in January for ineffective leadership and poor performance.
In Mr Zatko's damning revelations, first revealed by CNN and The Washington Post, he accused Twitter of failing to maintain stringent security practices and "lying about bots to Elon Musk".
He filed his complaint with the Securities and Exchange Commission in July. The BBC has seen a redacted copy of the complaint shared via CBS news.
In it, Mr Zatko also criticised the way in which Twitter handled sensitive information and claimed that it has failed to accurately report some of these matters to US regulators.
Twitter has faced a number of high profile hacks with Barack Obama, Joe Biden and Kanye West all targeted.
Among his concerns Mr Zatko alleges that Twitter suffered from an usually high rate of security incidents - "approximately one security incident each week serious enough that Twitter was required to report it to regulators".
He said that so-called insider threats - security risks posed by people with malicious intent from within the company - went "virtually unmonitored".
The former security chief revealed his concern about how Twitter handled data, alleging that too many employees had access to sensitive systems and user data.
He worried that the company had no workable disaster recovery plan, and claimed that in the past, Twitter had failed to properly delete the data of people who cancelled their accounts.
More about: