diff --git a/back/api/auth.js b/back/api/auth.js
index d137163..3a739cc 100644
--- a/back/api/auth.js
+++ b/back/api/auth.js
@@ -7,6 +7,11 @@ const router = express.Router();
 
 router.post('/login', async (req, res) => {
     const { username, password } = req.body;
+
+    if (!username || !password) {
+        return res.status(400).send({ error: 'Invalid username or password' });
+    }
+
     const connection = await getConnection();
     const user = await getUserByUsername(connection, username);
     connection.end();
@@ -25,6 +30,11 @@ router.post('/register', async (req, res) => {
     const { username, password } = req.body;
     const connection = await getConnection();
 
+    if (!username || !password) {
+        connection.end();
+        return res.status(400).send({ error: 'Invalid username or password' });
+    }
+
     const user = await getUserByUsername(connection, username);
     if (user[0]) {
         connection.end();
@@ -44,7 +54,17 @@ router.post('/register', async (req, res) => {
 
 router.post('/me', async (req, res) => {
     const { token } = req.body;
+
+    if (!token) {
+        return res.status(400).send({ error: 'Invalid token' });
+    }
+
     const decoded = jwt.verify(token, process.env.JWT_SECRET);
+
+    if (!decoded.id) {
+        return res.status(400).send({ error: 'Invalid token' });
+    }
+
     const connection = await getConnection();
     const users = await getUser(connection, decoded.id);
     connection.end();
diff --git a/back/api/channels.js b/back/api/channels.js
index 11a1c5d..912b044 100644
--- a/back/api/channels.js
+++ b/back/api/channels.js
@@ -62,6 +62,11 @@ router.post('/:name/messages/send', async (req, res) => {
 router.post('/:name/messages/delete', async (req, res) => {
     const { token, message_id } = req.body;
     const name = req.params.name;
+
+    if (!message_id || !token) {
+        return res.status(400).send({ error: 'Missing parameters' });
+    }
+
     const connection = await getConnection();
 
     const decoded = jwt.verify(token, process.env.JWT_SECRET);
@@ -89,6 +94,11 @@ router.post('/:name/messages/delete', async (req, res) => {
 
 router.post('/add', async (req, res) => {
     const { name, description, token } = req.body;
+
+    if (!name || !description || !token) {
+        return res.status(400).send({ error: 'Missing parameters' });
+    }
+
     const connection = await getConnection();
 
     const decoded = jwt.verify(token, process.env.JWT_SECRET);
diff --git a/back/libs/mysql.js b/back/libs/mysql.js
index 60b452a..16a3262 100644
--- a/back/libs/mysql.js
+++ b/back/libs/mysql.js
@@ -12,7 +12,8 @@ function getConnection() {
 function getUser(connection, id) {
   return new Promise((resolve, reject) => {
     connection.query(
-      `SELECT * FROM users WHERE id = ${id}`,
+      `SELECT * FROM users WHERE id = ?`,
+      [id], // Use parameterized query
       (error, result) => {
         if (error) {
           reject(new Error(error));
@@ -24,23 +25,25 @@ function getUser(connection, id) {
 }
 
 function getUserByUsername(connection, username) {
-    return new Promise((resolve, reject) => {
-        connection.query(
-        `SELECT * FROM users WHERE username = '${username}'`,
-        (error, result) => {
-            if (error) {
-            reject(new Error(error));
-            }
-            resolve(result);
+  return new Promise((resolve, reject) => {
+    connection.query(
+      `SELECT * FROM users WHERE username = ?`,
+      [username], // Use parameterized query
+      (error, result) => {
+        if (error) {
+          reject(new Error(error));
         }
-        );
-    });
+        resolve(result);
+      }
+    );
+  });
 }
 
 function addUser(connection, username, password) {
   return new Promise((resolve, reject) => {
     connection.query(
-      `INSERT INTO users (username, password) VALUES ('${username}', '${password}')`,
+      `INSERT INTO users (username, password) VALUES (?, ?)`,
+      [username, password], // Use parameterized query
       (error, result) => {
         if (error) {
           reject(new Error(error));
@@ -52,17 +55,23 @@ function addUser(connection, username, password) {
 }
 
 function getUserLastMessages(connection, username) {
-    return new Promise((resolve, reject) => {
-        connection.query(
-        `SELECT messages.id, user_id, username, content, date, channels.name AS channel_name FROM messages JOIN users ON messages.user_id = users.id JOIN channels ON messages.channel_id = channels.id WHERE username = "${username}" ORDER BY date DESC LIMIT 5`,
-        (error, result) => {
-            if (error) {
-            reject(new Error(error));
-            }
-            resolve(result);
+  return new Promise((resolve, reject) => {
+    connection.query(
+      `SELECT messages.id, user_id, username, content, date, channels.name AS channel_name 
+       FROM messages 
+       JOIN users ON messages.user_id = users.id 
+       JOIN channels ON messages.channel_id = channels.id 
+       WHERE username = ? 
+       ORDER BY date DESC LIMIT 5`,
+      [username], // Use parameterized query
+      (error, result) => {
+        if (error) {
+          reject(new Error(error));
         }
-        );
-    });
+        resolve(result);
+      }
+    );
+  });
 }
 
 function getChannels(connection) {
@@ -82,7 +91,11 @@ function getChannels(connection) {
 function getChannel(connection, name) {
   return new Promise((resolve, reject) => {
     connection.query(
-      `SELECT channels.id, name, description, owner_id, username AS owner_username FROM channels JOIN users ON channels.owner_id = users.id WHERE name = "${name}"`,
+      `SELECT channels.id, name, description, owner_id, username AS owner_username 
+       FROM channels 
+       JOIN users ON channels.owner_id = users.id 
+       WHERE name = ?`,
+      [name], // Use parameterized query
       (error, result) => {
         if (error) {
           reject(new Error(error));
@@ -94,73 +107,86 @@ function getChannel(connection, name) {
 }
 
 function addChannel(connection, name, description, owner_id) {
-    return new Promise((resolve, reject) => {
-        connection.query(
-        `INSERT INTO channels (name, description, owner_id) VALUES ('${name}', '${description}', ${owner_id})`,
-        (error, result) => {
-            if (error) {
-            reject(new Error(error));
-            }
-            resolve(result);
+  return new Promise((resolve, reject) => {
+    connection.query(
+      `INSERT INTO channels (name, description, owner_id) VALUES (?, ?, ?)`,
+      [name, description, owner_id], // Use parameterized query
+      (error, result) => {
+        if (error) {
+          reject(new Error(error));
         }
-        );
-    });
+        resolve(result);
+      }
+    );
+  });
 }
 
 function getMessages(connection, channel_id) {
-    return new Promise((resolve, reject) => {
-        connection.query(
-        `SELECT messages.id, user_id, username, content, date, channels.name AS channel_name FROM messages JOIN users ON messages.user_id = users.id JOIN channels ON messages.channel_id = channels.id WHERE channel_id = ${channel_id} ORDER BY date DESC`,
-        (error, result) => {
-            if (error) {
-            reject(new Error(error));
-            }
-            resolve(result);
+  return new Promise((resolve, reject) => {
+    connection.query(
+      `SELECT messages.id, user_id, username, content, date, channels.name AS channel_name 
+       FROM messages 
+       JOIN users ON messages.user_id = users.id 
+       JOIN channels ON messages.channel_id = channels.id 
+       WHERE channel_id = ? 
+       ORDER BY date DESC`,
+      [channel_id], // Use parameterized query
+      (error, result) => {
+        if (error) {
+          reject(new Error(error));
         }
-        );
-    });
+        resolve(result);
+      }
+    );
+  });
 }
 
 function getLastMessages(connection) {
-    return new Promise((resolve, reject) => {
-        connection.query(
-        `SELECT messages.id, user_id, username, content, date, channels.name AS channel_name FROM messages JOIN users ON messages.user_id = users.id JOIN channels ON messages.channel_id = channels.id ORDER BY date DESC LIMIT 5`,
-        (error, result) => {
-            if (error) {
-            reject(new Error(error));
-            }
-            resolve(result);
+  return new Promise((resolve, reject) => {
+    connection.query(
+      `SELECT messages.id, user_id, username, content, date, channels.name AS channel_name 
+       FROM messages 
+       JOIN users ON messages.user_id = users.id 
+       JOIN channels ON messages.channel_id = channels.id 
+       ORDER BY date DESC LIMIT 5`,
+      (error, result) => {
+        if (error) {
+          reject(new Error(error));
         }
-        );
-    });
+        resolve(result);
+      }
+    );
+  });
 }
 
 function addMessage(connection, channel_id, user_id, message) {
-    return new Promise((resolve, reject) => {
-        connection.query(
-        `INSERT INTO messages (channel_id, user_id, content, date) VALUES (${channel_id}, ${user_id}, "${message}", ${Math.floor(Date.now() / 1000)})`,
-        (error, result) => {
-            if (error) {
-            reject(new Error(error));
-            }
-            resolve(result);
+  return new Promise((resolve, reject) => {
+    connection.query(
+      `INSERT INTO messages (channel_id, user_id, content, date) VALUES (?, ?, ?, ?)`,
+      [channel_id, user_id, message, Math.floor(Date.now() / 1000)], // Use parameterized query
+      (error, result) => {
+        if (error) {
+          reject(new Error(error));
         }
-        );
-    });
+        resolve(result);
+      }
+    );
+  });
 }
 
 function deleteMessage(connection, message_id) {
-    return new Promise((resolve, reject) => {
-        connection.query(
-        `DELETE FROM messages WHERE id = ${message_id}`,
-        (error, result) => {
-            if (error) {
-            reject(new Error(error));
-            }
-            resolve(result);
+  return new Promise((resolve, reject) => {
+    connection.query(
+      `DELETE FROM messages WHERE id = ?`,
+      [message_id], // Use parameterized query
+      (error, result) => {
+        if (error) {
+          reject(new Error(error));
         }
-        );
-    });
+        resolve(result);
+      }
+    );
+  });
 }
 
 module.exports = {