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How I pulled data out of a cross-origin iframe I couldn't touch
TL;DR: A developer shares how they extracted data from a cross-origin iframe they couldn’t modify, turning a seemingly simple export task into a two-day debugging and data-splitting effort. They ultimately intercepted a private API and parsed a large blob to access the flashcard data.
The story begins with a straightforward goal: export flashcards to Anki. Initial DOM inspection failed as the cards render inside a cross-origin iframe, making selectors ineffective. The author traces the DOM, discovers the iframe is served from a different domain, and pieces together a workaround by intercepting network calls to a private Google API and manually parsing a 1.5MB blob. The experience highlights the challenges of cross-origin isolation when scraping or extracting data from third-party embeds, and the persistence required to reveal hidden data. The takeaway is to anticipate cross-origin boundaries and plan for more involved data extraction when necessary.
Question for the room: Have you run into cross-origin iframe data access in your projects, and what techniques did you use to safely and ethically extract the needed data?
— via dev.to
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