fix: avoid sed interpolation when prepending log summary

Use a temporary file to write the summary header and existing log content, then replace the original log atomically. This removes the dependency on sed for summary insertion and avoids unsafe string interpolation.

bin/netupgrade

@@ -10,7 +10,7 @@ showHelp() {
 }
 
 checkDependencies() {
-	local -a REQUIRED_CMDS=(ssh whiptail sed tee rm touch)
+	local -a REQUIRED_CMDS=(ssh whiptail cat tee rm touch)
 	local -a MISSING_CMDS=()
 	local CMD
 
@@ -84,6 +84,22 @@ runSSH() {
 	ssh "${SSH_USER}@${HOST}" "$@"
 }
 
+prependLogSummary() {
+	local SUMMARY_CONTENT="${1}"
+	local TEMP_LOGFILENAME="${LOGFILENAME}.tmp"
+
+	{
+		echo "Results :"
+		echo "---------"
+		echo ""
+		echo -e "${SUMMARY_CONTENT}"
+		echo ""
+		echo ""
+		cat "${LOGFILENAME}"
+	} > "${TEMP_LOGFILENAME}"
+	mv "${TEMP_LOGFILENAME}" "${LOGFILENAME}"
+}
+
 selectNodes(){
 	local -a OPTIONS=()
 	local -a SELECTED_ITEMS=()
@@ -152,9 +168,7 @@ selectNodes(){
 		done
 	done
 
-	sed -i "1s/^/${RESULT//\//\\\/}\n\n\n\n/" "${LOGFILENAME}"
-	sed -i "1s/^/---------\n\n/" "${LOGFILENAME}"
-	sed -i "1s/^/Results :\n/" "${LOGFILENAME}"
+	prependLogSummary "${RESULT}"
 	if [ -n "${LOGVIEWER}" ]; then
 		"${LOGVIEWER}" "${LOGFILENAME}"
 	else