Google has fixed this issue. Please see our new coverage on this issue, the bug details, and the fix. Original article below, albeit somewhat outdated now.
Google has halted the rollout of Chrome 79 on Android after mobile app developers reported a major bug that was deleting user data and resetting mobile apps.
The bug occurred during the update process from Chrome 78 to Chrome 79. In Chrome 79, Google developers changed the location of the Chrome directory.
In a bug report filed last week, Google developers admitted to making a mistake with this operation and forgetting to move the contents of localStorage or WebSQL into the new Chrome 79 directory, making the data inaccessible for all users.
localStorage and WebSQL are widely used in mobile apps
Both localStorage and WebSQL are storage mechanisms that allow a website or web app to store data on a user's device, inside a user's Chrome profile directory.
While some websites use localStorage or WebSQL, most prefer to use dedicated database servers to store user data on the server-side.
However, localStorage and WebSQL are widely used on mobile devices, and especially by mobile app developers.
These days, many Android apps are nothing more than a website loaded inside the WebView component -- a stripped-down version of Chrome.
These apps heavily depend on mechanisms like localStorage or WebSQL to save settings and user data locally, instead of using a separate and bulkier SQLite database.
When Chrome 79 started rolling out, these apps lost access to all the files and data saved inside the old Chrome 78 localStorage and WebSQL folders.
App users lost data, settings, files, and even access to their accounts.
"When I say 'broken,' I mean that their encrypted login information has been wiped and they can't remember their credentials (and resetting them are practically impossible in the case of our app)," said the developer of a mobile cash management app. In his case, over 250,000 users have been affected already, with two million more facing a similar problem in the coming days. However, he is not alone. There are countless other Android app developers who are facing similar issues.
And for good reasons, app users are getting angry. Unfortunately, they're getting angry at the wrong persons -- namely, the app developers, not knowing this is a Chrome issue.
"My app currently get[sic] review bombed with 1-star ratings because all users lose[sic] currently all stored data," said another app dev on Reddit.
A fix is not 100% guaranteed to save restore user data
Chrome 79 was released on Tuesday, December 10. A first bug report was filed on Thursday, and Google stopped the Chrome 79 rollout on Android on Saturday. Unfortunately, the update already reached around 50% of the Android userbase, meaning it already caused quite a lot of breakage.
Google developers are currently working on an update that fixes the data migration process, but for many, this might be too late.
Even Google developers don't know if the older localStorage and WebSQL files were left behind, or the Chrome update process wiped the data. In some cases, "cleaner aps" might have deleted the data after the update operation.
Further, moving the old files to the new location might end up overwriting new files the user has created in the meantime, leading again to data loss.
A solution for the bug is still being discussed on the Chromium bug tracker.