I've had for a long time a site with the famous Recent Tweets Widget. The plugin came as part of a theme, and back in the day, it included translation .po and .mo files for French language. I didn't pay attention to this before.
But recently I have found that the strings indicating the tweet's age (x days/months ago, etc.) are translated into Spanish, main language of the site. I have confirmed that the translated strings are not in the .po files, neither from the plugin nor from the site translations. So I assume they come fron an external site. I couldn't tell the exact date when it happened.
Digging about this oddity, I've found that translations can now be managed in http://translations.wordpress.org. And in this site, the aforementioned plugin exists, with 8 translations (a specially bad one for Spanish). My guess is somehow WP could be recovering this translation from the site, via REST API or similar. But I can't find any specific call for this in the code.
I wonder if the __() function has now the ability to recover external translations for a given text domain, or, in the shape of a question: what could be the possible sources for this "ghost" translation? Thanks in advance.