Hi Eric,
Thank you for contacting Blue Prism Community.
This is a classic Blue Prism pain point — the Windows Security credential prompt (used for NTLM/Basic proxy or site auth) is often rendered as a XAML-hosted dialog rather than plain Win32 controls, which is why neither Win32 nor AA spying picks up individual elements like the Cancel button, and why a separate "Attacher" object fails to bind to it.
A few approaches that reliably work in practice:
1. Switch spy mode to UI Automation (UIA), not Win32/Active Accessibility
In Application Modeller, when you go to identify the Cancel button, try changing the element type to UIA (sometimes labelled "Win32" vs "UIA" vs "AA" depending on your BP version). This dialog is built on the Credential UI framework, which exposes its buttons through UI Automation even when the Win32 hook sees only the parent host window. This is usually the fix — try it first.
2. If UIA also can't drill in, skip element identification entirely and use keystrokes
A plain Escape keypress or Alt+F4 closes this dialog exactly like clicking Cancel, since it's a modal foreground window.
Use a Navigate stage → Send Hotkey, or a Global Send Keys action, targeted at the window by title ("Windows Security") rather than trying to attach to an element inside it.
This avoids the attach problem completely since you're acting on the window handle, not a child control.
3. Last resort — region/image click
If none of the above work (rare, but possible if the dialog is on a secure/isolated desktop, which sometimes happens depending on GPO settings for credential prompts), define a Region relative to the dialog and use image-based click on the Cancel button. This is fragile across DPI/resolution changes, so treat it as a fallback rather than the primary method.
I'd start with #1, since it fixes the underlying identification problem rather than working around it — but #2 (Escape/Alt+F4 via hotkey targeting the window) is the pragmatic route most people end up using for this specific dialog since it's fast to implement and very reliable.
Regards
Hossein Azimi (APJ Team Member)
