Opening a downloaded file in the web browser and then restarting the app results in a blank screen and "Denying unprivileged request" console error

[data-sync-user]

Blank screen:

!Blank Screen.jpeg|width=393,height=852,alt="Blank Screen.jpeg"!

Steps to Reproduce:

• You must use a ﹍real physical device﹍ (NOT a simulator… could only reproduce on my iPhone 15 running iOS 17.6.1)
• Download a PDF in the browser
• Navigate to the Downloads panel
• Tap the PDF you just downloaded. This will open it in your current tab.
• Quit and restart the app.

Expected Behaviour:

• Either we can still preview the PDF file…
• OR we should see the tab before we reviewed the PDF file

Actual Behaviour:

• A blank screen.
• The toolbar displays a file://... URL with the name of the PDF file.
• Console error for developers: “Denying unprivileged request…”

Note: If you go Back with the toolbar button to the previous webpage, and then Forward again, the file displays correctly. However, switching tabs does not “fix” it, only this.

---

The blank screen is because we are hitting the following code block in BrowserViewController+WebViewDelegates.swift:

if InternalURL.isValid(url: url) {
            if navigationAction.navigationType != .backForward,
               navigationAction.isInternalUnprivileged,
               !url.isReaderModeURL {
                logger.log("Denying unprivileged request: \(navigationAction.request)",
                           level: .warning,
                           category: .webview)
                decisionHandler(.cancel)
                return
            }

            decisionHandler(.allow)
            return
        }

NOTE: This applies to all downloaded files with a MIME type in webViewViewableTypes:

private static let webViewViewableTypes: [String] = [
        MIMEType.Bitmap,
        MIMEType.GIF,
        MIMEType.JPEG,
        MIMEType.HTML,
        MIMEType.PDF,
        MIMEType.PlainText,
        MIMEType.PNG,
        MIMEType.WebP
]

Demo:

[^RPReplay_Final1732830612.MP4]

!File vs Blank Screen.PNG|width=1179,height=2556,alt="File vs Blank Screen.PNG"!

┆Issue is synchronized with this Jira Bug