Incident: Booking.com Bug Causes iOS Universal Links Failure on iPhones

Published Date: 2016-03-30

Postmortem Analysis
Timeline 1. The software failure incident happened on March 29, 2016, as reported in Article 41561.
System 1. Booking.com app (specifically a recent version with a large 2.3MB file of URLs) [41561] 2. iOS's linking system (Universal Links) on the iPhone and iPad [41561]
Responsible Organization 1. Booking.com - The bug that caused the software failure incident was due to an error in the travel planning app Booking.com [41561].
Impacted Organization 1. Apple smartphone and tablet users [41561]
Software Causes 1. The software failure incident was caused by a bug in the travel planning app Booking.com, which overloaded Apple's core system for linking web addresses and apps within iOS on the iPhone and iPad, called Universal Links [41561].
Non-software Causes 1. The bug was caused by an error in the travel planning app Booking.com, which overloaded one of Apple’s core systems for linking web addresses and apps within iOS on the iPhone and iPad, called Universal Links [41561].
Impacts 1. Links and web addresses not working, causing iPhones to crash for thousands of Apple smartphone and tablet users [41561]. 2. Users experiencing terrible battery life and finding their iPhones practically unusable [41561]. 3. Inability to open links in various apps such as Safari, Mail, Messages, Twitter, etc. [41561]. 4. Frustration and anger among users towards Apple and the iOS 9.3 update [41561]. 5. Users resorting to alternative search engines like Bing due to the issue [41561]. 6. Some users finding temporary fixes by using third-party browsers or disabling JavaScript in Safari [41561]. 7. Need for Apple to release a software update to fix the problem for affected users [41561].
Preventions 1. Proper testing and quality assurance procedures by Booking.com before releasing the app update could have prevented the software failure incident [41561]. 2. Implementing better error handling mechanisms within the app to prevent such large files from breaking iOS's linking system could have helped avoid the issue [41561]. 3. Apple could have conducted more thorough testing of the iOS update, especially considering the large number of beta versions released, to catch and rectify the issue before it affected users [41561].
Fixes 1. Booking.com fixed its app to address the bug that caused the software failure incident [41561]. 2. Apple acknowledged the issue and stated that they would release a fix in a software update soon [41561].
References 1. Apple spokesperson [41561]

Software Taxonomy of Faults

Category Option Rationale
Recurring one_organization, multiple_organization (a) The software failure incident related to the bug causing links and web addresses not to work and iPhones to crash happened at Booking.com. The bug in the Booking.com app overloaded Apple's core system for linking web addresses and apps within iOS, leading to the malfunction of the Universal Links system on iPhones and iPads [41561]. (b) The software failure incident also affected multiple organizations and their products and services. Users reported that the bug caused issues not only within the Booking.com app but also in various other apps and platforms such as Mail, Messages, Safari, Twitter, and Google searches made within Safari. This widespread impact indicates that the incident had repercussions beyond just the Booking.com app and Apple's iOS system, affecting multiple organizations and their services [41561].
Phase (Design/Operation) design (a) The software failure incident in this case was primarily due to a design issue. The bug was caused by an error in the travel planning app Booking.com, which overloaded one of Apple’s core systems for linking web addresses and apps within iOS on the iPhone and iPad, called Universal Links. The issue stemmed from a recent version of the app that came with a large 2.3MB file filled with thousands of individual URLs, breaking iOS’s linking system [41561]. This design flaw in the app's implementation of Universal Links led to the failure affecting thousands of Apple smartphone and tablet users. (b) The operation of the system, in this case, did not contribute directly to the software failure incident. Users who installed and ran the app before it was fixed ended up with a broken Universal Link system, causing links not to work within various Apple and third-party apps. However, the root cause of the issue was the design flaw in the app itself, rather than any operational misuse by the users [41561].
Boundary (Internal/External) within_system, outside_system (a) The software failure incident in this case was primarily within the system. The issue was caused by a bug in the travel planning app Booking.com, specifically an error in the app's Universal Links file that overloaded Apple's core system for linking web addresses and apps within iOS on iPhones and iPads [41561]. The bug resulted in links not working and iPhones crashing for thousands of users who had installed the app before it was fixed. Apple acknowledged the problem and mentioned that they would release a fix in a software update soon [41561].
Nature (Human/Non-human) non-human_actions, human_actions (a) The software failure incident in this case was primarily caused by a bug in the travel planning app Booking.com, which overloaded Apple's core system for linking web addresses and apps within iOS on the iPhone and iPad, known as Universal Links. The bug was a result of a recent version of the app containing a large 2.3MB file with thousands of individual URLs, which was significantly larger than the typical Universal Links files found in most apps. This non-human action of including an unusually large file led to the breaking of iOS's linking system, causing links and web addresses not to work and iPhones to crash for thousands of users [41561]. (b) On the other hand, some users expressed frustration and blamed Apple and the recent iOS 9.3 update for the software failure incident. They criticized the company for allowing such a bug to affect their devices, with one user mentioning that after seven betas of iOS 9.3, such issues should not occur. This highlights the aspect of human actions, such as software development, testing, and release processes, that may have contributed to the bug not being caught earlier or properly addressed before impacting users [41561].
Dimension (Hardware/Software) software (a) The software failure incident in this case was primarily due to a software issue. The problem was caused by a bug in the travel planning app Booking.com, which overloaded one of Apple's core systems for linking web addresses and apps within iOS on the iPhone and iPad, called Universal Links. This bug resulted from a recent version of the app containing a large 2.3MB file with thousands of individual URLs, breaking iOS's linking system [41561]. (b) The software failure incident was not attributed to hardware issues but rather to a software bug in the Booking.com app that caused the malfunction in Apple's Universal Links system [41561].
Objective (Malicious/Non-malicious) non-malicious (a) The software failure incident described in the articles is non-malicious. The issue was caused by a bug in the travel planning app Booking.com, which inadvertently overloaded Apple's core system for linking web addresses and apps within iOS. This bug resulted in links not working and iPhones crashing for thousands of users. The incident was not a deliberate act to harm the system but rather a consequence of a large file size in the app that broke iOS's linking system [41561].
Intent (Poor/Accidental Decisions) poor_decisions (a) The software failure incident related to the bug causing links and web addresses not to work on iPhones and iPads was primarily due to poor_decisions made by the developers of the travel planning app Booking.com. The app included a large 2.3MB file with thousands of individual URLs for Universal Links, which was significantly larger than the usual size for such files. This decision to include such a large file overloaded Apple's core systems, leading to the failure affecting thousands of users [41561].
Capability (Incompetence/Accidental) development_incompetence, accidental (a) The software failure incident in this case was primarily due to development incompetence. The bug that caused links and web addresses not to work and iPhones to crash was a result of an error in the travel planning app Booking.com. The app included a large 2.3MB file with thousands of individual URLs for Universal Links, which overloaded Apple's core systems. This error in the app's development led to the disruption of the linking system within iOS, affecting various Apple and third-party apps [41561]. (b) Additionally, the incident could also be considered accidental as it was not intentional but rather a consequence of the error in the app's development process. The large file size of the Universal Links file in the app was not deliberately meant to cause the system overload but was a mistake that led to the software failure incident affecting thousands of users [41561].
Duration temporary The software failure incident described in the article was temporary. The issue was caused by a bug in the Booking.com app that overloaded Apple's core system for linking web addresses and apps within iOS. Users who installed and ran the app before it was fixed ended up with a broken Universal Link system, causing most links to not work when tapped within various apps. Users found temporary solutions such as using third-party browsers or disabling JavaScript in Safari to get some links working again. Additionally, some users found that rebooting their iPhones temporarily remedied the problem. Apple acknowledged the issue and stated that they would release a fix in a software update soon, indicating that the failure was not permanent [41561].
Behaviour crash, omission, other (a) crash: The software failure incident in this case resulted in iPhones crashing. Users found their iPhones practically unusable after the bug caused the Universal Link system to break, leading to links not working when tapped within various apps [41561]. (b) omission: The bug caused links not to work within various Apple and third-party apps, including Mail, Messages, Safari, Twitter, and others. Users were unable to open links, leading to an omission of the intended function of the system [41561]. (c) timing: There is no specific mention of the software failure incident being related to timing issues in terms of the system performing its intended functions too late or too early. (d) value: The software failure incident did not involve the system performing its intended functions incorrectly. (e) byzantine: The software failure incident did not involve the system behaving erroneously with inconsistent responses and interactions. (f) other: The other behavior observed in this software failure incident was the system experiencing terrible battery life for some users after the bug occurred, which impacted the overall usability of the iPhones [41561].

IoT System Layer

Layer Option Rationale
Perception None None
Communication None None
Application None None

Other Details

Category Option Rationale
Consequence property, delay (d) property: People's material goods, money, or data was impacted due to the software failure The software failure incident caused iPhones and iPads to crash and become practically unusable for some users. Additionally, the bug resulted in the Universal Link system being broken, leading to most links not working when tapped within Apple and third-party apps like Mail, Messages, Safari, and Twitter. This issue impacted users' ability to access information and services, potentially affecting their daily activities and interactions [41561].
Domain information (a) The software failure incident affected the information industry as it was related to a bug in the travel planning app Booking.com, which caused links and web addresses not to work on iPhones and iPads [Article 41561].

Sources

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