I Hid a Watermark in Screenshots, and iOS Thought It Was a Password

Screenshots were the app's biggest sign-up channel, so I built a watermark that's invisible in the app but appears when users take a screenshot, using iOS's secure text entry flag, which strips content from screenshots to protect passwords. It worked. It also made iOS think every chat message was a password field, breaking autocorrect and triggering "Save to Keychain" prompts. Fix: drop the UITextField entirely and set the underlying disableUpdateMask flag directly on a CALayer via reflection (with the private-API name base64-encoded to survive App Store review). Same screenshot-hiding behavior, no password heuristic firing. Lesson: iOS has way more hidden heuristics reading your view hierarchy than you'd expect, and private APIs are a recurring tax, not a one-time cost.