system
A chat on /r/wallstreetbets
human
First sentence:  
  
 &gt; As part of a routine security review in January, we found that some user  passwords were being stored in a readable format within our internal  data storage systems.  
  
 'Some' users equals: 
  
 &gt; We estimate that we will notify hundreds of millions of Facebook Lite  users, tens of millions of other Facebook users, and tens of thousands  of Instagram users.  
  
 &amp;#x200B;

gpt
Readable format != Plaintext though. 
  
 &amp;#x200B; 
  
 It could be a proprietary binary blob that they were storing it, but instead found it encoded in hex strings? 
  
 &amp;#x200B; 
  
 This is not a data leak, just a security audit found a portion of data wasn't using the proprietary system.