--- a/mobile/android/geckoview/api.txt
+++ b/mobile/android/geckoview/api.txt
@@ -394,16 +394,17 @@ package org.mozilla.geckoview {
     method @UiThread public void onShutdown();
   }
 
   @UiThread public static interface GeckoRuntime.ServiceWorkerDelegate {
     method @UiThread @NonNull public GeckoResult<GeckoSession> onOpenWindow(@NonNull String);
   }
 
   @AnyThread public final class GeckoRuntimeSettings extends RuntimeSettings {
+    method public boolean getAboutConfigEnabled();
     method @NonNull public String[] getArguments();
     method public boolean getAutomaticFontSizeAdjustment();
     method public int getAutoplayDefault();
     method @Nullable public String getConfigFilePath();
     method public boolean getConsoleOutputEnabled();
     method @NonNull public ContentBlocking.Settings getContentBlocking();
     method @Nullable public Class<?> getCrashHandler();
     method @Nullable public Float getDisplayDensityOverride();
@@ -420,16 +421,17 @@ package org.mozilla.geckoview {
     method public int getPreferredColorScheme();
     method public boolean getRemoteDebuggingEnabled();
     method @Nullable public GeckoRuntime getRuntime();
     method @Nullable public Rect getScreenSizeOverride();
     method @Nullable public RuntimeTelemetry.Delegate getTelemetryDelegate();
     method public boolean getUseContentProcessHint();
     method public boolean getUseMaxScreenDepth();
     method public boolean getWebFontsEnabled();
+    method @NonNull public GeckoRuntimeSettings setAboutConfigEnabled(boolean);
     method @NonNull public GeckoRuntimeSettings setAutomaticFontSizeAdjustment(boolean);
     method @NonNull public GeckoRuntimeSettings setAutoplayDefault(int);
     method @NonNull public GeckoRuntimeSettings setConsoleOutputEnabled(boolean);
     method @NonNull public GeckoRuntimeSettings setDoubleTapZoomingEnabled(boolean);
     method @NonNull public GeckoRuntimeSettings setFontInflationEnabled(boolean);
     method @NonNull public GeckoRuntimeSettings setFontSizeFactor(float);
     method @NonNull public GeckoRuntimeSettings setGlMsaaLevel(int);
     method @NonNull public GeckoRuntimeSettings setInputAutoZoomEnabled(boolean);
@@ -443,16 +445,17 @@ package org.mozilla.geckoview {
     field public static final int COLOR_SCHEME_DARK = 1;
     field public static final int COLOR_SCHEME_LIGHT = 0;
     field public static final int COLOR_SCHEME_SYSTEM = -1;
     field public static final Parcelable.Creator<GeckoRuntimeSettings> CREATOR;
   }
 
   @AnyThread public static final class GeckoRuntimeSettings.Builder extends RuntimeSettings.Builder {
     ctor public Builder();
+    method @NonNull public GeckoRuntimeSettings.Builder aboutConfigEnabled(boolean);
     method @NonNull public GeckoRuntimeSettings.Builder arguments(@NonNull String[]);
     method @NonNull public GeckoRuntimeSettings.Builder automaticFontSizeAdjustment(boolean);
     method @NonNull public GeckoRuntimeSettings.Builder autoplayDefault(int);
     method @NonNull public GeckoRuntimeSettings.Builder configFilePath(@Nullable String);
     method @NonNull public GeckoRuntimeSettings.Builder consoleOutput(boolean);
     method @NonNull public GeckoRuntimeSettings.Builder contentBlocking(@NonNull ContentBlocking.Settings);
     method @NonNull public GeckoRuntimeSettings.Builder crashHandler(@Nullable Class<?>);
     method @NonNull public GeckoRuntimeSettings.Builder debugLogging(boolean);

--- a/mobile/android/geckoview/src/androidTest/java/org/mozilla/geckoview/test/RuntimeSettingsTest.kt
+++ b/mobile/android/geckoview/src/androidTest/java/org/mozilla/geckoview/test/RuntimeSettingsTest.kt
@@ -8,16 +8,19 @@ import android.provider.Settings
 import android.support.test.InstrumentationRegistry
 import android.support.test.filters.MediumTest
 import android.support.test.runner.AndroidJUnit4
 import org.hamcrest.Matchers.*
 import org.junit.Ignore
 import org.junit.Test
 import org.junit.runner.RunWith
 import kotlin.math.roundToInt
+import org.mozilla.geckoview.GeckoSession
+import org.mozilla.geckoview.test.rule.GeckoSessionTestRule.AssertCalled
+import org.mozilla.geckoview.test.util.Callbacks
 
 @RunWith(AndroidJUnit4::class)
 @MediumTest
 class RuntimeSettingsTest : BaseSessionTest() {
 
     @Ignore("disable test for frequently failing Bug 1538430")
     @Test fun automaticFontSize() {
         val settings = sessionRule.runtime.settings
@@ -134,9 +137,39 @@ class RuntimeSettingsTest : BaseSessionT
 
         settings.fontSizeFactor = 1.0f
         prefValue = (sessionRule.getPrefs(fontInflationPref)[0] as Int)
         assertThat("Gecko font inflation pref remains turned off",
                 prefValue, `is`(0))
         assertThat("GeckoRuntimeSettings remains turned off",
                 settings.fontInflationEnabled, `is`(false))
     }
+
+    @Test
+    @Ignore // Bug 1582150
+    fun aboutConfig() {
+        val settings = sessionRule.runtime.settings;
+
+        assertThat("about:config should be disabled by default",
+                settings.aboutConfigEnabled, equalTo(false))
+        mainSession.delegateDuringNextWait(object : Callbacks.ProgressDelegate {
+            @AssertCalled
+            override fun onPageStop(session: GeckoSession, success: Boolean) {
+                assertThat("about:config load should fail", success, equalTo(false))
+            }
+        })
+
+        mainSession.loadUri("about:config")
+        mainSession.waitForPageStop()
+
+        settings.aboutConfigEnabled = true
+
+        mainSession.delegateDuringNextWait(object : Callbacks.ProgressDelegate {
+            @AssertCalled
+            override fun onPageStop(session: GeckoSession, success: Boolean) {
+                assertThat("about:config load should succeed", success, equalTo(true))
+            }
+        })
+
+        mainSession.loadUri("about:config")
+        mainSession.waitForPageStop()
+    }
 }

--- a/mobile/android/geckoview/src/main/java/org/mozilla/geckoview/GeckoRuntimeSettings.java
+++ b/mobile/android/geckoview/src/main/java/org/mozilla/geckoview/GeckoRuntimeSettings.java
@@ -400,16 +400,30 @@ public final class GeckoRuntimeSettings 
          * @return This Builder instance.
          */
         public @NonNull Builder debugLogging(final boolean enable) {
             getSettings().mDevToolsConsoleToLogcat.set(enable);
             getSettings().mConsoleServiceToLogcat.set(enable);
             getSettings().mGeckoViewLogLevel.set(enable ? "Debug" : "Fatal");
             return this;
         }
+
+        /**
+         * Sets whether or not about:config should be enabled. This is a page that allows
+         * users to directly modify Gecko preferences. Modification of some preferences may
+         * cause the app to break in unpredictable ways -- crashes, performance issues, security
+         * vulnerabilities, etc.
+         *
+         * @param flag True if about:config should be enabled, false otherwise.
+         * @return This Builder instance.
+         */
+        public @NonNull Builder aboutConfigEnabled(final boolean flag) {
+            getSettings().mAboutConfig.set(flag);
+            return this;
+        }
     }
 
     private GeckoRuntime mRuntime;
     /* package */ boolean mUseContentProcess;
     /* package */ String[] mArgs;
     /* package */ Bundle mExtras;
     /* package */ String mConfigFilePath;
 
@@ -444,16 +458,18 @@ public final class GeckoRuntimeSettings 
     /* package */ final Pref<Boolean> mTelemetryEnabled = new Pref<>(
             "toolkit.telemetry.geckoview.streaming", false);
     /* package */ final Pref<String> mGeckoViewLogLevel = new Pref<>(
             "geckoview.logging", "Debug");
     /* package */ final Pref<Boolean> mConsoleServiceToLogcat = new Pref<>(
             "consoleservice.logcat", true);
     /* package */ final Pref<Boolean> mDevToolsConsoleToLogcat = new Pref<>(
             "devtools.console.stdout.chrome", true);
+    /* package */ final Pref<Boolean> mAboutConfig = new Pref<>(
+            "general.aboutConfig.enable", false);
 
     /* package */ boolean mDebugPause;
     /* package */ boolean mUseMaxScreenDepth;
     /* package */ float mDisplayDensityOverride = -1.0f;
     /* package */ int mDisplayDpiOverride;
     /* package */ int mScreenWidthOverride;
     /* package */ int mScreenHeightOverride;
     /* package */ Class<? extends Service> mCrashHandler;
@@ -1018,16 +1034,39 @@ public final class GeckoRuntimeSettings 
         mGlMsaaLevel.commit(level);
         return this;
     }
 
     public @Nullable RuntimeTelemetry.Delegate getTelemetryDelegate() {
         return mTelemetryProxy.getDelegate();
     }
 
+    /**
+     * Gets whether about:config is enabled or not.
+     *
+     * @return True if about:config is enabled, false otherwise.
+     */
+    public boolean getAboutConfigEnabled() {
+        return mAboutConfig.get();
+    }
+
+    /**
+     * Sets whether or not about:config should be enabled. This is a page that allows
+     * users to directly modify Gecko preferences. Modification of some preferences may
+     * cause the app to break in unpredictable ways -- crashes, performance issues, security
+     * vulnerabilities, etc.
+     *
+     * @param flag True if about:config should be enabled, false otherwise.
+     * @return This GeckoRuntimeSettings instance.
+     */
+    public @NonNull GeckoRuntimeSettings setAboutConfigEnabled(final boolean flag) {
+        mAboutConfig.commit(flag);
+        return this;
+    }
+
     @Override // Parcelable
     public void writeToParcel(final Parcel out, final int flags) {
         super.writeToParcel(out, flags);
 
         ParcelableUtils.writeBoolean(out, mUseContentProcess);
         out.writeStringArray(mArgs);
         mExtras.writeToParcel(out, flags);
         ParcelableUtils.writeBoolean(out, mDebugPause);

--- a/mobile/android/geckoview/src/main/java/org/mozilla/geckoview/doc-files/CHANGELOG.md
+++ b/mobile/android/geckoview/src/main/java/org/mozilla/geckoview/doc-files/CHANGELOG.md
@@ -24,27 +24,30 @@ exclude: true
   additional HTTP request headers.
 - Added support for exposing the content blocking log in [`ContentBlockingController`][71.7].({{bugzilla}}1580201)
 - ⚠️  Added `nativeApp` to [`WebExtension.MessageDelegate.onMessage`][71.8] which
   exposes the native application identifier that was used to send the message.
   ({{bugzilla}}1546445)
 - Added [`GeckoRuntime.ServiceWorkerDelegate`][71.9] set via
   ['setServiceWorkerDelegate'][71.10] to support ServiceWorkerClients.openWindow()
   ([bug 1511033]({{bugzilla}}1511033))
+- Added ['GeckoRuntimeSettings.Builder#aboutConfigEnabled'][71.11] to control whether or
+  not `about:config` should be available.
 
 [71.1]: {{javadoc_uri}}/RuntimeTelemetry.Delegate.html#onBooleanScalar-org.mozilla.geckoview.RuntimeTelemetry.Metric-
 [71.2]: {{javadoc_uri}}/RuntimeTelemetry.Delegate.html#onLongScalar-org.mozilla.geckoview.RuntimeTelemetry.Metric-
 [71.3]: {{javadoc_uri}}/RuntimeTelemetry.Delegate.html#onStringScalar-org.mozilla.geckoview.RuntimeTelemetry.Metric-
 [71.4]: {{javadoc_uri}}/RuntimeTelemetry.Delegate.html#onHistogram-org.mozilla.geckoview.RuntimeTelemetry.Metric-
 [71.5]: {{javadoc_uri}}/RuntimeTelemetry.Metric.html
 [71.6]: {{javadoc_uri}}/GeckoSession.html#loadUri-java.lang.String-java.io.File-java.util.Map-
 [71.7]: {{javadoc_uri}}/ContentBlockingController.html
 [71.8]: {{javadoc_uri}}/WebExtension.MessageDelegate.html#onMessage-java.lang.String-java.lang.Object-org.mozilla.geckoview.WebExtension.MessageSender-
 [71.9]: {{javadoc_uri}}/GeckoRuntime.ServiceWorkerDelegate.html
 [71.10]: {{javadoc_uri}}/GeckoRuntime#setServiceWorkerDelegate-org.mozilla.geckoview.GeckoRuntime.ServiceWorkerDelegate-
+[71.11]: {{javadoc_uri}}/GeckoRuntimeSettings.Builder.html#aboutConfigEnabled-boolean-
 
 ## v70
 - Added API for session context assignment
   [`GeckoSessionSettings.Builder.contextId`][70.1] and deletion of data related
   to a session context [`StorageController.clearDataForSessionContext`][70.2].
   ([bug 1501108]({{bugzilla}}1501108))
 - Removed `setSession(session, runtime)` from [`GeckoView`][70.5]. With this
   change, `GeckoView` will no longer manage opening/closing of the
@@ -357,9 +360,9 @@ exclude: true
 [65.19]: {{javadoc_uri}}/GeckoSession.NavigationDelegate.LoadRequest.html#isRedirect
 [65.20]: {{javadoc_uri}}/GeckoSession.html#LOAD_FLAGS_BYPASS_CLASSIFIER    
 [65.21]: {{javadoc_uri}}/GeckoSession.ContentDelegate.ContextElement.html
 [65.22]: {{javadoc_uri}}/GeckoSession.ContentDelegate.html#onContextMenu-org.mozilla.geckoview.GeckoSession-int-int-org.mozilla.geckoview.GeckoSession.ContentDelegate.ContextElement-
 [65.23]: {{javadoc_uri}}/GeckoSession.FinderResult.html
 [65.24]: {{javadoc_uri}}/CrashReporter.html#sendCrashReport-android.content.Context-android.os.Bundle-java.lang.String-
 [65.25]: {{javadoc_uri}}/GeckoResult.html
 
-[api-version]: ec6b45461c040d8dc76aa0fed4917b3c4c07d67e
+[api-version]: 16e050b1d50a9909b936c740a94220eaff4115a3

--- a/mobile/android/geckoview_example/src/main/java/org/mozilla/geckoview_example/GeckoViewActivity.java
+++ b/mobile/android/geckoview_example/src/main/java/org/mozilla/geckoview_example/GeckoViewActivity.java
@@ -176,17 +176,18 @@ public class GeckoViewActivity extends A
                     .consoleOutput(true)
                     .contentBlocking(new ContentBlocking.Settings.Builder()
                         .antiTracking(ContentBlocking.AntiTracking.DEFAULT |
                                       ContentBlocking.AntiTracking.STP)
                         .safeBrowsing(ContentBlocking.SafeBrowsing.DEFAULT)
                         .cookieBehavior(ContentBlocking.CookieBehavior.ACCEPT_NON_TRACKERS)
                         .build())
                     .crashHandler(ExampleCrashHandler.class)
-                    .telemetryDelegate(new ExampleTelemetryDelegate());
+                    .telemetryDelegate(new ExampleTelemetryDelegate())
+                    .aboutConfigEnabled(true);
 
             sGeckoRuntime = GeckoRuntime.create(this, runtimeSettingsBuilder.build());
 
             sGeckoRuntime.getWebExtensionController().setTabDelegate(new WebExtensionController.TabDelegate() {
                 @Override
                 public GeckoResult<GeckoSession> onNewTab(WebExtension source, String uri) {
                     final TabSession newSession = createSession();
                     mToolbarView.updateTabCount();