Phia Accused of Cookie Stuffing, Claiming Affiliate Commissions It Did Not Earn

Quick Facts

• Phia, an AI shopping browser extension co-founded by Phoebe Gates, raised $43.5 million and reached 1.5 million users before the allegations surfaced.
• Bloomberg, Capital One Shopping, and independent researcher Ben Edelman each separately found that Phia’s mobile extension opened invisible background tabs to override other publishers’ affiliate codes during checkout.
• Phia acknowledged a “misattribution” issue within 24 hours of the findings going public and said it has since resolved the problem.

Phia, a venture-backed AI shopping assistant, is accused of cookie stuffing — a form of affiliate fraud in which a browser extension secretly places tracking codes on a user’s device to claim sales commissions it did not earn.

The allegations come from separate investigations by Bloomberg, Capital One Shopping, and independent affiliate marketing researcher Ben Edelman, each of whom found that Phia’s mobile browser extension opened an invisible background tab during checkout, inserted the company’s affiliate code, and closed the tab within seconds — all without user interaction.

In one Bloomberg test, clicking a Nordstrom link inside a Wirecutter article triggered Phia’s extension to silently replace Wirecutter’s referral code with its own. The same behavior appeared when clicking a Google ad originating from a different publisher’s site.

The mechanism works differently on desktop browsers, where background tabs are visible at the top of the screen. On mobile, tab switching is hidden behind a button, making the auto-click effectively invisible to most users mid-checkout.

A technical detail strengthens the case that the behavior was deliberate. The feature was controlled by a feature flag — a switch that engineers build, test, and deploy intentionally. That flag was always turned off for Chrome desktop users but remained active for iOS users. The code enabling the auto-click was introduced to Phia’s source code in December.

Ben Edelman, who has studied affiliate marketing fraud for years, said the practice crosses a clear line. “The most fundamental requirement in affiliate marketing is that commission is only paid if a user clicks,” Edelman said. “The rules don’t allow fake clicks, simulated clicks, imaginary clicks or hypothetical clicks.”

Capital One Shopping, which operates a competing browser extension, sent an email to retailers documenting its own findings. “Publishers like us are having material revenue taken,” the email stated. “And advertisers like you are losing money to fake clicks.”

Phia issued a public statement acknowledging the problem. “Within the last 24 hours, we were made aware that in a recent release our codebase was causing misattributions from a subset of users,” a company spokesperson said. “As soon as we were notified, our team worked overnight to identify, mitigate, and has since resolved the issue.”

The company framed the behavior as a bug rather than an intentional feature, but the use of a platform-specific feature flag complicates that characterization.

Phia launched in April 2025, co-founded by Phoebe Gates, daughter of Bill Gates, and her Stanford roommate Sophia Kianni. The app compares prices across new, resale, and luxury retail sites and calculates resale value before purchase. It takes a commission on sales through the platform.

The company raised an $8 million seed round from Kleiner Perkins in September 2025, followed by a $35.5 million Series A in January 2026 led by Notable Capital, with Khosla Ventures and Kleiner Perkins participating. The Series A valued Phia at roughly $185 million and attracted celebrity investors including Sydney Sweeney, Paris Hilton, and Khloé Kardashian, alongside tech backers such as Robinhood founder Vlad Tenev.

As of June, Phia reported 1.5 million users, nearly 10,000 retail brand partnerships, and more than 350 million products scanned. TIME named it one of the best inventions of 2025.

The cookie stuffing allegations put those brand relationships at risk. Retailers pay affiliate commissions believing those fees reward publishers who drove actual traffic to their sites. If Phia was claiming credit for sales generated by other publishers — including paid ads and editorial content — brands were effectively paying twice for the same customer.

The broader implication for software founders is a familiar governance risk: a feature flag toggled for one platform but not another, introduced months before public scrutiny, can become a reputational and legal liability fast. What gets built into a codebase and why is now a due diligence question for investors and partners alike.

Read more: Phia accused of ‘cookie stuffing,’ taking affiliate credit on purchases it didn’t earn