Chinese authorities revealed over the weekend that they have the capability of retrieving deleted messages from the almost universally used WeChat app. The admission doesn’t come as a surprise to many, but it’s rare for this type of questionable data collection tactic to be acknowledged publicly.As noted by the South China Morning Post, an anti-corruption commission in Hefei province posted Saturday to social media that it has “retrieved a series of deleted WeChat conversations from a subject” as part of an investigation.The post was deleted Sunday, but not before many had seen it and understood the ramifications. Tencent, which operates the WeChat service used by nearly a billion people (including myself), explained in a statement that “WeChat does not store any chat histories — they are only stored on users’ phones and computers.”The technical details of this storage were not disclosed, but it seems clear from the commission’s post that they are accessible in some way to interested authorities, as many have suspected for years. The app does, of course, comply with other government requirements, such as censoring certain topics.There are still plenty of questions, the answers to which would help explain user vulnerability: Are messages effectively encrypted at rest? Does retrieval require the user’s password and login, or can it be forced with a “master key” or backdoor? Can users permanently and totally delete messages on the WeChat platform at all?