Some Mac App Store Apps 'Damaged' Due to Expired Security Certificate
A growing number of MacRumors readers and Twitter users have been experiencing an issue with some Mac App Store apps displaying a "damaged" error when opened since late Wednesday. The issue has affected popular apps such as 1Password, Acorn, Byword, DaisyDisk and Tweetbot.
Mac users are prompted with this error message when opening Mac App Store apps:
“App Name” is damaged and can’t be opened. Delete “App Name” and download it again from the App Store.
Tweetbot developer Paul Haddad tweeted that the issue appears to be related to security certificates that expired on November 11, 2015, and he further speculated that the receipts now using SHA256 encryption may be causing problems with older OS X versions.
The issue, however, also appears to affect some users running OS X El Capitan, leading Haddad to believe that Mac App Store apps contacting Apple's servers simultaneously may be causing a "self inflicted DDOS on Apple’s receipt generation service."
Haddad says that rebooting your Mac on OS X 10.10 or later may resolve the issue, while some users have been forced to reinstall apps from the Mac App Store, disconnect from and reopen the Mac App Store or simply reenter their Apple ID password.
It appears that Apple has since set a new 2035 expiration date for the security certificates, per The Guardian, at least some for apps, but the issues are persisting for some. Apple did not respond to request for comment.
Update: Rene Ritchie at iMore has further explained what's causing Mac apps to report as "damaged" and what can be done about it.
Popular Stories
Apple is looking for a "breakthrough" with its push into wearable AI devices, including an "AirTag-sized pendant," according to Bloomberg's Mark Gurman.
In a report this week, he said the pendant is reminiscent of the failed Humane AI Pin, but it would be an iPhone accessory rather than a standalone product.
The pendant would feature an "always-on" camera and a microphone for Siri voice...
Apple will announce its rumored low-cost MacBook at its event on March 4, with the device coming in a selection of bold color options, according to a known leaker.
Earlier this week, Apple announced a "special Apple Experience" for the media in New York, London, and Shanghai, taking place on March 4, 2026 at 9:00am ET.
Posting on Weibo, the leaker known as "Instant Digital" said that the...
New trade-in data indicates that Apple's iPhone 17 Pro Max has rapidly become the single most traded-in smartphone.
According to a new report from SellCell, Apple's latest flagship iPhone has quickly risen to the top of the independent trade-in market, accounting for 11.5% of all devices appearing in the top-20 trade-in rankings just months after release. The analysis is based on SellCell...
Back at WWDC 2025, Apple revealed that it was planning to allow CarPlay users to watch video via AirPlay in their vehicles while they are not driving, and the first beta of iOS 26.4 suggests the feature may be nearing availability.
There are several new references to CarPlay video streaming functionality within the iOS 26.4 beta's source code. The feature is not yet visible to users, but...
Apple's iPhone development roadmap runs several years into the future and the company is continually working with suppliers on several successive iPhone models at the same time, which is why we often get rumored features months ahead of launch. The iPhone 18 series is no different, and we already have a good idea of what to expect for the iPhone 18 Pro and iPhone 18 Pro Max.
One thing worth...
