Now Patched 'Sign in With Apple' Bug Left Users Open to Attack

Researcher Bhavuk Jain in April discovered a critical Sign in With Apple vulnerability that could have resulted in a takeover of some user accounts. The bug was specific to third party apps that used Sign in With Apple and didn't implement additional security measures.

SigninwithApple e1590865553423
Jain notes that Sign in With Apple works by authenticating a user through a JWT (JSON Web Token) or a code that's generated by Apple's server. Apple then gives users the option to share either the email tied to their Apple ID or a private relay email address,which creates a JWT that's used to log in a user.

Jain then discovered that once JWTs for both Apple ID emails and private relay email addresses were requested and the token's signature was verified using Apple's public key, it "showed as valid." Should the bug have not been discovered, a JWT could be created and used to gain access to one's account.

In an interview with The Hacker News, Jain spoke about the severity of the bug:

The impact of the this vulnerability was quite critical as it could have allowed a full account takeover. Many developers have integrated Sign in with Apple since it is mandatory for applications that support other social logins. To name a few that use Sign in with Apple - Dropbox, Spotify, Airbnb, Giphy (now acquired by Facebook).

According to Jain, Apple conducted an investigation and concluded that no accounts were compromised using this method before the vulnerability was patched. Jain was paid $100,000 by Apple under its Apple Security Bounty Program for reporting the bug.

Popular Stories

Apple Logo Black

Apple Just Made Its Second-Biggest Acquisition Ever After Beats

Thursday January 29, 2026 10:07 am PST by
Apple today confirmed to Reuters that it has acquired Q.ai, an Israeli startup that is working on artificial intelligence technology for audio. Apple paid close to $2 billion for Q.ai, according to sources cited by the Financial Times. That would make this Apple's second-biggest acquisition ever, after it paid $3 billion for the popular headphone and audio brand Beats in 2014. Q.ai has...
imac video apple feature

Apple Unveils First New Products of 2026

Monday January 26, 2026 1:55 pm PST by
Apple today introduced its first two physical products of 2026: a second-generation AirTag and the Black Unity Connection Braided Solo Loop for the Apple Watch. Read our coverage of each announcement to learn more:Apple Unveils New AirTag With Longer Range, Louder Speaker, and More Apple Introduces New Black Unity Apple Watch BandBoth the new AirTag and the Black Unity Connection Braided...
iPhone 5s

iPhone 5s Gets New Software Update 13 Years After Launch

Monday January 26, 2026 3:56 pm PST by
Alongside iOS 26.2.1, Apple today released an updated version of iOS 12 for devices that are still running that operating system update, eight years after the software was first released. iOS 12.5.8 is available for the iPhone 5s and the iPhone 6, meaning Apple is continuing to support these devices for 13 and 12 years after launch, respectively. The iPhone 5s came out in September 2013,...
Apple Creator Studio

Apple's Next Launch is Today

Tuesday January 27, 2026 2:39 pm PST by
Update: Apple Creator Studio is now available. Apple Creator Studio launches this Wednesday, January 28. The all-in-one subscription provides access to the Final Cut Pro, Logic Pro, Pixelmator Pro, Motion, Compressor, and MainStage apps, with U.S. pricing set at $12.99 per month or $129 per year. A subscription to Apple Creator Studio also unlocks "intelligent features" and "premium...
apple silicon 1 feature

Apple Responds to Skyrocketing RAM and Storage Chip Prices

Thursday January 29, 2026 2:40 pm PST by
On an earnings call with equity analysts today, Apple CEO Tim Cook responded to fast-rising RAM and SSD storage chip prices in the supply chain. Prices for RAM and NAND storage chips are surging lately due to high demand from companies building out AI servers, resulting in supply constraints. Cook said that rising memory chip prices had a "minimal impact" on Apple's gross margin in the...

Top Rated Comments

SBlue1 Avatar
74 months ago
100,000? Well deserved. :)
Score: 13 Votes (Like | Disagree)
B4U Avatar
74 months ago
Are we getting numb with the constant SW issues that Apple is having lately?
Score: 11 Votes (Like | Disagree)
Peace Avatar
74 months ago
I’m getting burned out on timmys security problems .

windows is looking better
Score: 10 Votes (Like | Disagree)
I7guy Avatar
74 months ago

I’m getting burned out on timmys security problems .

windows is looking better
Windows is better? Sure windows is as tight as a drum as far as that goes.

Just keep patching them Timmy.
Score: 7 Votes (Like | Disagree)
cmaier Avatar
74 months ago

I don't care.

I'm done updating.

I'm sick and tired of my phone being artificially slowed.

I'm back to using Linux for things that need to be secure, like banking, etc.
You know this wasn’t a bug in the client software or operating system, right?
Score: 5 Votes (Like | Disagree)
konqerror Avatar
74 months ago

If it was unexploited and has been patched, there's not much of a story here… except to other businesses that might consider Sign In With Apple.
Bugs are a symptom, not the flaw. The constant stream of problems coming out from Apple shows their software development and QA processes are severely flawed.
Score: 5 Votes (Like | Disagree)