Few things here a) Focus doesn't have multi window support so I am not sure if this particular script is what I would consider UXSS b) You are trying to run javascript and want to control that in WKWebview, that isn't something directly possible unless we disable it as whole. Firefox (Desktop) does the same by opening in a new link. You see about:blank because in Focus we use the same webview and create one on top. I am not aware of any api that I can use that would help us intersect the request from that a() link
Bug 1855030 Comment 23 Edit History
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Few things here a) Focus doesn't have multi window support so I am not sure if this particular script is what I would consider UXSS b) You are trying to run javascript and want to control that in WKWebview, that isn't something directly possible unless we disable it as whole. Firefox (Desktop) does the same by opening in a new link. You see about:blank in Firefox desktop as its a new tab. However in Focus we use the same webview and create one on top of the same webview. I am not aware of any api that I can use that would help us intersect the request from that a() link