diff -r -U3 plasma-workspace-5.18.4.1.orig/startkde/startplasma.cpp plasma-workspace-5.18.4.1/startkde/startplasma.cpp
--- plasma-workspace-5.18.4.1.orig/startkde/startplasma.cpp	2020-03-31 17:33:37.000000000 +0300
+++ plasma-workspace-5.18.4.1/startkde/startplasma.cpp	2020-04-03 12:47:34.812587755 +0300
@@ -22,6 +22,8 @@
 #include <QStandardPaths>
 #include <QTextStream>
 #include <QDBusConnectionInterface>
+#include <QRegularExpression>
+#include <QProcessEnvironment>
 #include <KConfig>
 #include <KConfigGroup>
 
@@ -265,6 +267,16 @@
 // In that case, the update in startplasma might be too late.
 bool syncDBusEnvironment()
 {
+    const QRegularExpression re(QString::fromUtf8("[^A-Z0-9_]"));
+    const auto env = QProcessEnvironment::systemEnvironment();
+    for (const auto &key : env.keys()) {
+        const auto match = re.match(key);
+        if (match.hasMatch()) {
+//            qDebug() << "environment variable filtered:" << key;
+            qunsetenv(key.toUtf8().constData());
+        }
+    }
+
     int exitCode;
     // At this point all environment variables are set, let's send it to the DBus session server to update the activation environment
     if (!QStandardPaths::findExecutable(QStringLiteral("dbus-update-activation-environment")).isEmpty()) {