Apple Downloads of these Updates:
• Download macOS Catalina 10.15.5 Supplemental Update (1.02 GB)
  "provides important security updates and is recommended for all users."
  
  
• Download Security Update 2020-003 (High Sierra) (2.11 GB)
  (Now dated June 1, no change in listed download size. Should have been -004 or 003.1)

FYI: If you use Nvidia's web graphics drivers for 10.13.6, the Security Update new build number requires a driver update. (Update: See below for June 3rd Nvidia driver update download.)
 

"Installation Note: The installer requires System Preferences to be launched during the installation process. Do not manually close System Preferences until after clicking Allow in the Security & Privacy Preferences, later in the process.

The installer also requires rebooting the system after the installation process. Do not launch any other applications until the process is complete and the system has been rebooted.

New in Release 387.10.10.10.40.137"
(No new info, same notes on D/L page as previous drivers, so I won't repeat it here.)

Previous macOS Nvidia drivers are on our Mac Nvidia Drivers downloads page.

• Fixed the Battery Check test for iOS devices when using macOS 10.15.4 or greater and improved test performance for all supported macOS versions.
• Added support for MacBook Air (Retina, 13-inch, 2020), MacBook Pro (13-inch, 2020, Two Thunderbolt 3 Ports) and MacBook Pro (13-inch, 2020, Four Thunderbolt 3 Ports).
• Fixed issue where certain Mac models were reported as manufactured in 2010 instead of 2020.
• Updated Check Computer suites to default to the Intermediate suite.
• Updated the Bonjour device database for the Local Network tool.
• Updated the machine database for the Processor Check tool.
• Updated French, German, Italian, Japanese and Chinese (Simplified) localizations.
• Updated Macintosh identification strings for Check Computer.
• Updated Sparkle update framework to version 1.23.0.
• Other minor updates and enhancements.

• iOS 13.5.1 release notes.
• iPadOS 13.5.1 release notes.
  - Both updates "provide important security updates and is recommended for all users."
• About the security content of iOS 13.5.1 and iPadOS 13.5.1
  
  
• watchOS 6.2.6 release notes and security fixes.
  - "This update provides important security updates and is recommended for all users."
  
  
• tvOS 13.4.6 release notes and security fixes.
  - "includes general performance and stability improvements". (the usual note.)

• Micromat MachineProfile 1.3.15 update (use in-app update check)
  - Added MacBook Pro (13-inch, 2020, Two Thunderbolt 3 Ports) support.
  - Added MacBook Pro (13-inch, 2020, Four Thunderbolt 3 Ports) support.
  - Updated machine and location identification strings.
  - Other minor fixes and enhancements.
  
  
• Pixelmator Pro 1.6.4 (for macOS 10.13 or later, with 64-bit processor)
  - "Adds support for opening & exporting images in WebP format, and additional fixes."
  (See linked page for details.)

• How to Archive or make copies of the information you store in iCloud
  
  
• How to Locate backups of your iPhone, iPad, and iPod touch
  
  
• How to Manage your iCloud storage
  
  
• How to erase a disk for Mac (updated again June 9th)
  
  
• What to do before you sell, give away, or trade in your Mac
  
  
• How to Reset the System Management Controller (SMC) of your Mac
  
  
• How to reinstall macOS from macOS Recovery
  
  
• How to Restore your Mac from a backup
  
  
• How to use safe mode on your Mac

• Freeware VM VirtualBox version 6.1.10
  - See Change Log for list of fixes.
  
  
• Crucial 500GB P2 NVMe SSD Review (storagereview)
  
  
• 04.80.02 Firmware Update for 2019 LG B9 OLED TVs ("AirPlay improvements")
  - The "Applicable Models" list also includes many other LCD TVs.
  
  
• Download Apple's Windows Migration Assistant v2.2.0.0
  (System requirements lists macOS Mojave or later, Windows 7 or later.)