SANTA MONICA (AP) — Snapchat’s corporate parent disclosed Thursday that its ad sales are being hurt by a privacy crackdown that rolled out on Apple’s iPhones earlier this year, raising investor fears that the app’s financial growth is going into a tailspin.

The revelation in Snap Inc.’s third-quarter earnings report sparked a sell-off in after-hours trading that could foreshadow one of the biggest one-day drops in the company’s stock since it went public in 2017.

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Snap’s shares plunged by nearly 22% in Thursday’s extended trading. If that decrease is mirrored in Friday’s regular trading session, it will approach the stock’s previous one-day nadir in May 2018 when its price also plummeted by nearly 22%. A decline of that magnitude would wipe out nearly $30 billion in shareholder wealth.

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The alarms set off by Snap’s disappointing performance could foreshadow troubles for other apps that may be having more problems tracking their users online activities because of an Apple update to the iPhone’s iOS software released in April.

Stock prices of Facebook, Twitter and other companies reliant on digital ad revenue fell on word that Snap’s revenue was negatively impacted by new iOS privacy features.

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