diff --git a/index.bs b/index.bs
index fb5d1660..01fcbda2 100644
--- a/index.bs
+++ b/index.bs
@@ -2713,7 +2713,8 @@ The browser.createUserContext command creates a
browser.CreateUserContextParameters = {
? acceptInsecureCerts: bool,
- ? proxy: session.ProxyConfiguration
+ ? proxy: session.ProxyConfiguration,
+ ? unhandledPromptBehavior: session.UserPromptHandler
}
@@ -2747,6 +2748,10 @@ The [=remote end steps=] with |session| and |command parameters| are:
[=user context to accept insecure certificates override map=][|user context|]
to |acceptInsecureCerts|.
+1. If |command parameters| [=map/contains=] "unhandledPromptBehavior
",
+ [=map/set=] [=unhandled prompt behavior overrides map=][|user context|] to
+ |command parameters|["unhandledPromptBehavior
"].
+
1. If |command parameters| [=map/contains=] "proxy
":
1. Let |proxy configuration| be |command parameters|["proxy
"].
@@ -3115,11 +3120,22 @@ A viewport configuration is a [=struct=] with an [=struct/item=] name
viewport which is a [=viewport-configuration/viewport dimensions=]
or null and an [=struct/item=] named devicePixelRatio which is a float or null.
+An unhandled prompt behavior struct is a [=struct=] with:
+* [=struct/Item=] named alert which is a string or null;
+* [=struct/Item=] named beforeUnload which is a string or null;
+* [=struct/Item=] named confirm which is a string or null;
+* [=struct/Item=] named default which is a string or null;
+* [=struct/Item=] named file which is a string or null;
+* [=struct/Item=] named prompt which is a string or null.
+
A [=remote end=] has a viewport overrides map which is a weak map between [=user contexts=] and [=viewport configuration=].
A [=remote end=] has a locale overrides map which is a weak map between
[=navigables=] or [=user contexts=] and string or null.
+A [=remote end=] has an unhandled prompt behavior overrides map which is a
+weak map between [=user contexts=] and [=unhandled prompt behavior struct=].
+
### Types ### {#module-browsingcontext-types}
#### The browsingContext.BrowsingContext Type #### {#type-browsingContext-Browsingcontext}
@@ -5721,6 +5737,27 @@ closed steps given |window|, |type|, |accepted| and optional |user text|
+
"default"
] is not null,
+ return |unhandled prompt behavior override|["default"
].
+
+1. Let |handler configuration| be [=get the prompt handler=] with |type|.
+
+1. Return |handler configuration|'s [=prompt handler configuration/handler=].
+
+browsingContext.UserPromptOpenedParameters
production with the