--- a/toolkit/mozapps/extensions/AddonManager.jsm
+++ b/toolkit/mozapps/extensions/AddonManager.jsm
@@ -26,17 +26,16 @@ const PREF_DEFAULT_PROVIDERS_ENABLED  = 
 const PREF_EM_UPDATE_ENABLED          = "extensions.update.enabled";
 const PREF_EM_LAST_APP_VERSION        = "extensions.lastAppVersion";
 const PREF_EM_LAST_PLATFORM_VERSION   = "extensions.lastPlatformVersion";
 const PREF_EM_AUTOUPDATE_DEFAULT      = "extensions.update.autoUpdateDefault";
 const PREF_EM_STRICT_COMPATIBILITY    = "extensions.strictCompatibility";
 const PREF_EM_CHECK_UPDATE_SECURITY   = "extensions.checkUpdateSecurity";
 const PREF_APP_UPDATE_ENABLED         = "app.update.enabled";
 const PREF_APP_UPDATE_AUTO            = "app.update.auto";
-const UNKNOWN_XPCOM_ABI               = "unknownABI";
 
 const PREF_MIN_WEBEXT_PLATFORM_VERSION = "extensions.webExtensionsMinPlatformVersion";
 const PREF_WEBAPI_TESTING             = "extensions.webapi.testing";
 const PREF_WEBEXT_PERM_PROMPTS        = "extensions.webextPermissionPrompts";
 
 const UPDATE_REQUEST_VERSION          = 2;
 
 const XMLURI_BLOCKLIST                = "http://www.mozilla.org/2006/addons-blocklist";
@@ -1248,38 +1247,37 @@ var AddonManagerInternal = {
       throw Components.Exception("aAppVersion must be a string or null",
                                  Cr.NS_ERROR_INVALID_ARG);
 
     var addonStatus = aAddon.userDisabled || aAddon.softDisabled ? "userDisabled"
                                                                  : "userEnabled";
 
     if (!aAddon.isCompatible)
       addonStatus += ",incompatible";
-    if (aAddon.blocklistState == Ci.nsIBlocklistService.STATE_BLOCKED)
+
+    let {blocklistState} = aAddon;
+    if (blocklistState == Ci.nsIBlocklistService.STATE_BLOCKED)
       addonStatus += ",blocklisted";
-    if (aAddon.blocklistState == Ci.nsIBlocklistService.STATE_SOFTBLOCKED)
+    if (blocklistState == Ci.nsIBlocklistService.STATE_SOFTBLOCKED)
       addonStatus += ",softblocked";
 
-    try {
-      var xpcomABI = Services.appinfo.XPCOMABI;
-    } catch (ex) {
-      xpcomABI = UNKNOWN_XPCOM_ABI;
-    }
-
-    let uri = aUri.replace(/%ITEM_ID%/g, aAddon.id);
-    uri = uri.replace(/%ITEM_VERSION%/g, aAddon.version);
-    uri = uri.replace(/%ITEM_STATUS%/g, addonStatus);
-    uri = uri.replace(/%APP_ID%/g, Services.appinfo.ID);
-    uri = uri.replace(/%APP_VERSION%/g, aAppVersion ? aAppVersion :
-                                                      Services.appinfo.version);
-    uri = uri.replace(/%REQ_VERSION%/g, UPDATE_REQUEST_VERSION);
-    uri = uri.replace(/%APP_OS%/g, Services.appinfo.OS);
-    uri = uri.replace(/%APP_ABI%/g, xpcomABI);
-    uri = uri.replace(/%APP_LOCALE%/g, getLocale());
-    uri = uri.replace(/%CURRENT_APP_VERSION%/g, Services.appinfo.version);
+    let params = new Map(Object.entries({
+      ITEM_ID: aAddon.id,
+      ITEM_VERSION: aAddon.version,
+      ITEM_STATUS: addonStatus,
+      APP_ID: Services.appinfo.ID,
+      APP_VERSION: aAppVersion ? aAppVersion : Services.appinfo.version,
+      REQ_VERSION: UPDATE_REQUEST_VERSION,
+      APP_OS: Services.appinfo.OS,
+      APP_ABI: Services.appinfo.XPCOMABI,
+      APP_LOCALE: getLocale(),
+      CURRENT_APP_VERSION: Services.appinfo.version,
+    }));
+
+    let uri = aUri.replace(/%([A-Z_]+)%/g, (m0, m1) => params.get(m1) || m0);
 
     // escape() does not properly encode + symbols in any embedded FVF strings.
     return uri.replace(/\+/g, "%2B");
   },
 
   _updatePromptHandler(info) {
     let oldPerms = info.existingAddon.userPermissions;
     if (!oldPerms) {