Hello,
We are experiencing a behavior change with WKWebView related to upgradeKnownHostsToHTTPS.
Current application, we explicitly disable automatic HTTPS upgrades:
let config = WKWebViewConfiguration()
config.upgradeKnownHostsToHTTPS = false
Observed behavior
-
iOS 17.5 (built with Xcode 15.3)
http:// image URLs are not automatically upgraded to https://, and the behavior works as expected.
-
iOS 18.5 / 18.6.x (built with Xcode 16.4)
http:// image URLs appear to be automatically upgraded to https:// by WebKit, even when upgradeKnownHostsToHTTPS is explicitly set to false.
This behavior occurs for subresource requests such as <img src="http://..."> inside a WKWebView.
Question
- Has the behavior of upgradeKnownHostsToHTTPS changed in iOS 18 / Xcode 16?
- Is this property now ignored for certain types of subresource requests (e.g. images), or overridden by new WebKit security policies such as mixed-content HTTPS upgrades?
Any clarification or official guidance would be greatly appreciated!.