An `api.wordpress.org/core/version-check/1.7/` response example

{
	"offers": [
		{
			"response": "upgrade",
			"download": "https:\/\/downloads.wordpress.org\/release\/wordpress-6.4.3.zip",
			"locale": "en_US",
			"packages": {
				"full": "https:\/\/downloads.wordpress.org\/release\/wordpress-6.4.3.zip",
				"no_content": "https:\/\/downloads.wordpress.org\/release\/wordpress-6.4.3-no-content.zip",
				"new_bundled": "https:\/\/downloads.wordpress.org\/release\/wordpress-6.4.3-new-bundled.zip",
				"partial": false,
				"rollback": false
			},
			"current": "6.4.3",
			"version": "6.4.3",
			"php_version": "7.0.0",
			"mysql_version": "5.0",
			"new_bundled": "6.4",
			"partial_version": false
		},
		{
			"response": "autoupdate",
			"download": "https:\/\/downloads.wordpress.org\/release\/wordpress-6.4.3.zip",
			"locale": "en_US",
			"packages": {
				"full": "https:\/\/downloads.wordpress.org\/release\/wordpress-6.4.3.zip",
				"no_content": "https:\/\/downloads.wordpress.org\/release\/wordpress-6.4.3-no-content.zip",
				"new_bundled": "https:\/\/downloads.wordpress.org\/release\/wordpress-6.4.3-new-bundled.zip",
				"partial": false,
				"rollback": false
			},
			"current": "6.4.3",
			"version": "6.4.3",
			"php_version": "7.0.0",
			"mysql_version": "5.0",
			"new_bundled": "6.4",
			"partial_version": false,
			"new_files": true
		},
		{
			"response": "autoupdate",
			"download": "https:\/\/downloads.wordpress.org\/release\/wordpress-6.3.3.zip",
			"locale": "en_US",
			"packages": {
				"full": "https:\/\/downloads.wordpress.org\/release\/wordpress-6.3.3.zip",
				"no_content": "https:\/\/downloads.wordpress.org\/release\/wordpress-6.3.3-no-content.zip",
				"new_bundled": "https:\/\/downloads.wordpress.org\/release\/wordpress-6.3.3-new-bundled.zip",
				"partial": false,
				"rollback": false
			},
			"current": "6.3.3",
			"version": "6.3.3",
			"php_version": "7.0.0",
			"mysql_version": "5.0",
			"new_bundled": "6.4",
			"partial_version": false,
			"new_files": true
		},
		{
			"response": "autoupdate",
			"download": "https:\/\/downloads.wordpress.org\/release\/wordpress-6.2.4.zip",
			"locale": "en_US",
			"packages": {
				"full": "https:\/\/downloads.wordpress.org\/release\/wordpress-6.2.4.zip",
				"no_content": "https:\/\/downloads.wordpress.org\/release\/wordpress-6.2.4-no-content.zip",
				"new_bundled": "https:\/\/downloads.wordpress.org\/release\/wordpress-6.2.4-new-bundled.zip",
				"partial": false,
				"rollback": false
			},
			"current": "6.2.4",
			"version": "6.2.4",
			"php_version": "5.6.20",
			"mysql_version": "5.0",
			"new_bundled": "6.4",
			"partial_version": false,
			"new_files": true
		},
		{
			"response": "autoupdate",
			"download": "https:\/\/downloads.wordpress.org\/release\/wordpress-6.1.5.zip",
			"locale": "en_US",
			"packages": {
				"full": "https:\/\/downloads.wordpress.org\/release\/wordpress-6.1.5.zip",
				"no_content": "https:\/\/downloads.wordpress.org\/release\/wordpress-6.1.5-no-content.zip",
				"new_bundled": "https:\/\/downloads.wordpress.org\/release\/wordpress-6.1.5-new-bundled.zip",
				"partial": false,
				"rollback": false
			},
			"current": "6.1.5",
			"version": "6.1.5",
			"php_version": "5.6.20",
			"mysql_version": "5.0",
			"new_bundled": "6.4",
			"partial_version": false,
			"new_files": true
		},
		{
			"response": "autoupdate",
			"download": "https:\/\/downloads.wordpress.org\/release\/wordpress-6.0.7.zip",
			"locale": "en_US",
			"packages": {
				"full": "https:\/\/downloads.wordpress.org\/release\/wordpress-6.0.7.zip",
				"no_content": "https:\/\/downloads.wordpress.org\/release\/wordpress-6.0.7-no-content.zip",
				"new_bundled": "https:\/\/downloads.wordpress.org\/release\/wordpress-6.0.7-new-bundled.zip",
				"partial": false,
				"rollback": false
			},
			"current": "6.0.7",
			"version": "6.0.7",
			"php_version": "5.6.20",
			"mysql_version": "5.0",
			"new_bundled": "6.4",
			"partial_version": false,
			"new_files": true
		},
		{
			"response": "autoupdate",
			"download": "https:\/\/downloads.wordpress.org\/release\/wordpress-5.9.9.zip",
			"locale": "en_US",
			"packages": {
				"full": "https:\/\/downloads.wordpress.org\/release\/wordpress-5.9.9.zip",
				"no_content": "https:\/\/downloads.wordpress.org\/release\/wordpress-5.9.9-no-content.zip",
				"new_bundled": "https:\/\/downloads.wordpress.org\/release\/wordpress-5.9.9-new-bundled.zip",
				"partial": false,
				"rollback": false
			},
			"current": "5.9.9",
			"version": "5.9.9",
			"php_version": "5.6.20",
			"mysql_version": "5.0",
			"new_bundled": "6.4",
			"partial_version": false,
			"new_files": true
		},
		{
			"response": "autoupdate",
			"download": "https:\/\/downloads.wordpress.org\/release\/wordpress-5.8.9.zip",
			"locale": "en_US",
			"packages": {
				"full": "https:\/\/downloads.wordpress.org\/release\/wordpress-5.8.9.zip",
				"no_content": "https:\/\/downloads.wordpress.org\/release\/wordpress-5.8.9-no-content.zip",
				"new_bundled": "https:\/\/downloads.wordpress.org\/release\/wordpress-5.8.9-new-bundled.zip",
				"partial": "https:\/\/downloads.wordpress.org\/release\/wordpress-5.8.9-partial-3.zip",
				"rollback": "https:\/\/downloads.wordpress.org\/release\/wordpress-5.8.9-rollback-3.zip"
			},
			"current": "5.8.9",
			"version": "5.8.9",
			"php_version": "5.6.20",
			"mysql_version": "5.0",
			"new_bundled": "6.4",
			"partial_version": "5.8.3",
			"new_files": false
		}
	],
	"translations": []
}

How is version checking implemented in WordPress?