diff --git a/projects/packages/protect-status/changelog/fix-php-undefined-array-key-warning b/projects/packages/protect-status/changelog/fix-php-undefined-array-key-warning
new file mode 100644
index 0000000000000..72562089ff171
--- /dev/null
+++ b/projects/packages/protect-status/changelog/fix-php-undefined-array-key-warning
@@ -0,0 +1,4 @@
+Significance: patch
+Type: fixed
+
+Fix PHP warnings caused by uninstalled extensions.
diff --git a/projects/packages/protect-status/src/class-scan-status.php b/projects/packages/protect-status/src/class-scan-status.php
index 32deca2eba526..6f743cc397b63 100644
--- a/projects/packages/protect-status/src/class-scan-status.php
+++ b/projects/packages/protect-status/src/class-scan-status.php
@@ -243,7 +243,7 @@ private static function normalize_api_data( $scan_data ) {
 
 				// Theme and Plugin Threats
 				if ( ! empty( $scan_threat->extension ) && in_array( $scan_threat->extension->type, array( 'plugin', 'theme' ), true ) ) {
-					$installed_extension = 'plugin' === $scan_threat->extension->type ? $plugins[ $scan_threat->extension->slug ] : $themes[ $scan_threat->extension->slug ];
+					$installed_extension = 'plugin' === $scan_threat->extension->type ? ( $plugins[ $scan_threat->extension->slug ] ?? null ) : ( $themes[ $scan_threat->extension->slug ] ?? null );
 
 					// If the extension is no longer installed, skip this threat.
 					// todo: use version_compare()