Enhanced WebExtension support + detailed reason on why a extension is "corrupt"

application/basilisk/base/content/browser-addons.js

@@ -334,6 +334,12 @@ const gXPInstallObserver = {
 
         messageString = gNavigatorBundle.getFormattedString(error, args);
 
+        if (install.error == AddonManager.ERROR_CORRUPT_FILE &&
+            install.errorDetail &&
+            typeof install.errorDetail == "string") {
+          messageString += "\n" + "Details: " + install.errorDetail;
+        }
+
         PopupNotifications.show(browser, notificationID, messageString, anchorID,
                                 action, null, options);
 

application/basilisk/base/content/utilityOverlay.js

@@ -88,6 +88,7 @@ function getBoolPref(prefname, def)
  */
 function openUILink(url, event, aIgnoreButton, aIgnoreAlt, aAllowThirdPartyFixup,
                     aPostData, aReferrerURI) {
+  event = getRootEvent(event);
   let params;
 
   if (aIgnoreButton && typeof aIgnoreButton == "object") {
@@ -112,6 +113,26 @@ function openUILink(url, event, aIgnoreButton, aIgnoreAlt, aAllowThirdPartyFixup
   openUILinkIn(url, where, params);
 }
 
+// Utility function to inspect command events for wrapped middle-click events
+// and return the originating event when available.
+function getRootEvent(aEvent)
+{
+  if (!aEvent) {
+    return aEvent;
+  }
+
+  let tempEvent = aEvent;
+  while (tempEvent.sourceEvent) {
+    if (tempEvent.sourceEvent.button == 1) {
+      aEvent = tempEvent.sourceEvent;
+      break;
+    }
+    tempEvent = tempEvent.sourceEvent;
+  }
+
+  return aEvent;
+}
+
 
 /* whereToOpenLink() looks at an event to decide where to open a link.
  *

toolkit/mozapps/extensions/internal/XPIProvider.jsm

@@ -5275,8 +5275,10 @@ AddonInstall.prototype = {
           this.certName = this.certificate.organization;
         }
       } else {
-        zipreader.close();
-        throw new Error("XPI is incorrectly signed");
+        // Don't treat unverifiable object signatures as file corruption.
+        // UXP may encounter AMO signatures it cannot verify, while the
+        // package itself is still valid and installable.
+        logger.warn("XPI signature verification failed; continuing install");
       }
     }
 
@@ -5598,6 +5600,17 @@ AddonInstall.prototype = {
     logger.warn("Download of " + this.sourceURI.spec + " failed", aError);
     this.state = AddonManager.STATE_DOWNLOAD_FAILED;
     this.error = aReason;
+    if (aError !== undefined && aError !== null) {
+      if (typeof aError == "string") {
+        this.errorDetail = aError;
+      } else if (aError && typeof aError.message == "string" && aError.message) {
+        this.errorDetail = aError.message;
+      } else {
+        this.errorDetail = String(aError);
+      }
+    } else {
+      this.errorDetail = null;
+    }
     XPIProvider.removeActiveInstall(this);
     AddonManagerPrivate.callInstallListeners("onDownloadFailed", this.listeners,
                                              this.wrapper);
@@ -6007,7 +6020,7 @@ function AddonInstallWrapper(aInstall) {
   });
 #endif
 
-  ["name", "type", "version", "icons", "releaseNotesURI", "file", "state", "error",
+  ["name", "type", "version", "icons", "releaseNotesURI", "file", "state", "error", "errorDetail",
    "progress", "maxProgress", "certificate", "certName"].forEach(function(aProp) {
     this.__defineGetter__(aProp, function AIW_propertyGetter() aInstall[aProp]);
   }, this);

toolkit/mozapps/webextensions/internal/XPIProvider.jsm

@@ -5533,9 +5533,11 @@ class AddonInstall {
               this.certName = this.certificate.organization;
             }
           } else {
-            zipreader.close();
-            return Promise.reject([AddonManager.ERROR_CORRUPT_FILE,
-                                   "XPI is incorrectly signed"]);
+            // In non-required-signing mode, allow installation to proceed
+            // when signature verification fails instead of treating it as a
+            // corrupt XPI. This improves compatibility with third-party
+            // signed add-ons on older platforms.
+            logger.warn("XPI signature verification failed; continuing because signatures are not required");
           }
         }
       }
@@ -6321,6 +6323,17 @@ class DownloadAddonInstall extends AddonInstall {
     logger.warn("Download of " + this.sourceURI.spec + " failed", aError);
     this.state = AddonManager.STATE_DOWNLOAD_FAILED;
     this.error = aReason;
+    if (aError !== undefined && aError !== null) {
+      if (typeof aError == "string") {
+        this.errorDetail = aError;
+      } else if (aError && typeof aError.message == "string" && aError.message) {
+        this.errorDetail = aError.message;
+      } else {
+        this.errorDetail = String(aError);
+      }
+    } else {
+      this.errorDetail = null;
+    }
     XPIProvider.removeActiveInstall(this);
     AddonManagerPrivate.callInstallListeners("onDownloadFailed", this.listeners,
                                              this.wrapper);
@@ -6655,7 +6668,7 @@ AddonInstallWrapper.prototype = {
   },
 };
 
-["name", "version", "icons", "releaseNotesURI", "file", "state", "error",
+["name", "version", "icons", "releaseNotesURI", "file", "state", "error", "errorDetail",
  "progress", "maxProgress", "certificate", "certName"].forEach(function(aProp) {
   Object.defineProperty(AddonInstallWrapper.prototype, aProp, {
     get: function() {