diff --git a/NEWS b/NEWS
index 83965ccf..52a106fc 100644
--- a/NEWS
+++ b/NEWS
@@ -105,6 +105,20 @@ have already been considered.
     (mostly reverted)
 //////////////////////////////////////////////////////////////////////
 
+ELinks 0.12pre5.GIT now:
+------------------------
+
+To be released as 0.12pre6 or 0.12rc1.
+
+Bugs that should be removed from NEWS before the 0.12.0 release:
+
+* critical bug 943: Don't let user JavaScripts call any methods of
+  ``elinks.action'' in tabs that do not have the focus.  If a tab was
+  closed with ``elinks.action.tab_close'' while it had pop-up windows,
+  ELinks could crash; as a precaution, don't allow other actions
+  either.  ELinks 0.12pre1 was the first release that supported
+  ``elinks.action''.
+
 ELinks 0.12pre5:
 ----------------
 
diff --git a/doc/smjs-scripting.txt b/doc/smjs-scripting.txt
index 34221cd4..155136ad 100644
--- a/doc/smjs-scripting.txt
+++ b/doc/smjs-scripting.txt
@@ -234,9 +234,10 @@ A history item has these properties:
 *Compatibility:* ELinks 0.12pre1
 
 NOTE: When you read an action function from this hash, ELinks binds it to the
-current tab; any later calls to the function affect that tab.  This may be
-changed in a future version.  It is safest to call the function right away,
-rather than save it in a variable and call it later.
+current tab; any later calls to the function throw errors if that tab no
+longer has the focus (in its terminal).  This may be changed in a future
+version.  It is safest to call the function right away, rather than save it
+in a variable and call it later.
 --
 
 [[smjs-elinks.keymaps]] elinks.keymaps (hash)::
diff --git a/src/scripting/smjs/action_object.c b/src/scripting/smjs/action_object.c
index 330e21f1..db3203f7 100644
--- a/src/scripting/smjs/action_object.c
+++ b/src/scripting/smjs/action_object.c
@@ -8,9 +8,11 @@
 
 #include "config/kbdbind.h"
 #include "ecmascript/spidermonkey-shared.h"
+#include "intl/gettext/libintl.h"
 #include "scripting/smjs/core.h"
 #include "scripting/smjs/elinks_object.h"
 #include "session/session.h"
+#include "terminal/window.h"
 #include "util/memory.h"
 #include "viewer/action.h"
 
@@ -66,6 +68,32 @@ smjs_action_fn_callback(JSContext *ctx, uintN argc, jsval *rval)
 		return JS_TRUE;
 	}
 
+	if (!would_window_receive_keypresses(hop->ses->tab)) {
+		/* The user cannot run actions in this tab by pressing
+		 * keys, and some actions could crash if run in this
+		 * situation; so we don't let user scripts run actions
+		 * either.
+		 *
+		 * In particular, this check should fix bug 943, where
+		 * ::ACT_MAIN_TAB_CLOSE called destroy_session(),
+		 * which freed struct type_query while BFU dialogs had
+		 * pointers to it.  That crash could be prevented in
+		 * various ways but it seems other similar crashes are
+		 * possible, e.g. if the link menu is open and has a
+		 * pointer to a session that is then destroyed.
+		 * Instead of thoroughly auditing the use of pointers
+		 * to sessions and related structures, I'll just
+		 * disable the feature, to bring the ELinks 0.12
+		 * release closer.
+		 *
+		 * The "%s" prevents interpretation of any percent
+		 * signs in translations.  */
+		JS_ReportError(ctx, "%s",
+			       _("Cannot run actions in a tab that doesn't "
+				 "have the focus", hop->ses->tab->term));
+		return JS_FALSE; /* make JS propagate the exception */
+	}
+
 	if (argc >= 1) {
 		int32 val;
 
diff --git a/src/terminal/window.c b/src/terminal/window.c
index b1cf4ad6..f7b1452d 100644
--- a/src/terminal/window.c
+++ b/src/terminal/window.c
@@ -219,3 +219,25 @@ set_dlg_window_ptr(struct dialog_data *dlg_data, struct window *window, int x, i
 	}
 	set_window_ptr(window, x, y);
 }
+
+#if CONFIG_SCRIPTING_SPIDERMONKEY
+/** Check whether keypress events would be directed to @a win.  */
+int
+would_window_receive_keypresses(const struct window *win)
+{
+	struct terminal *const term = win->term;
+	const struct window *selected;
+
+	/* At least @win must be in the list.  */
+	assert(!list_empty(term->windows));
+	if_assert_failed return 0;
+
+	selected = term->windows.next;
+	if (selected->type != WINDOW_TAB) return 0;
+
+	selected = get_current_tab(term);
+	if (selected != win) return 0;
+
+	return 1;
+}
+#endif	/* CONFIG_SCRIPTING_SPIDERMONKEY */
diff --git a/src/terminal/window.h b/src/terminal/window.h
index 0069d7e4..14651a81 100644
--- a/src/terminal/window.h
+++ b/src/terminal/window.h
@@ -100,4 +100,8 @@ void assert_window_stacking(struct terminal *);
 #define assert_window_stacking(t) ((void) (t))
 #endif
 
+#if CONFIG_SCRIPTING_SPIDERMONKEY
+int would_window_receive_keypresses(const struct window *);
+#endif
+
 #endif