diff --git a/ipynbsrv/web/templates/web/collaborationgroups/modal_addusers.html b/ipynbsrv/web/templates/web/collaborationgroups/modal_addusers.html
index 81d3fa6..82fde3c 100644
--- a/ipynbsrv/web/templates/web/collaborationgroups/modal_addusers.html
+++ b/ipynbsrv/web/templates/web/collaborationgroups/modal_addusers.html
@@ -14,7 +14,7 @@ <h4 class="modal-title">Add users</h4>
                     <div class="form-group">
                         <label for="users">Members</label>
                         <div class="select">
-                            <select class="enableMultiselectCaseInsensitiveFiltering" multiple="multiple" name="users">
+                            <select class="enableMultiselectCaseInsensitiveFiltering" multiple="multiple" name="users" required>
                                 {% for user in users %}
                                     {% if user.backend_user and user.backend_user.id not in group.member_ids %}
                                         <option value="{{ user.id }}">{{ user.username }}</option>
diff --git a/ipynbsrv/web/templates/web/containers/modal_create.html b/ipynbsrv/web/templates/web/containers/modal_create.html
index 73940bc..8a938b0 100644
--- a/ipynbsrv/web/templates/web/containers/modal_create.html
+++ b/ipynbsrv/web/templates/web/containers/modal_create.html
@@ -23,7 +23,7 @@ <h4 class="modal-title">New container</h4>
                         <label for="image">Image</label>
                         <div class="select">
 	                        <select name="image_id" class="form-control enableCaseInsensitiveFiltering" required>
-	                            <option>None</option>
+	                            <option value="" selected>None</option>
 	                            {% for img in images %}
 	                                <option value="{{ img.id }}">{{ img.friendly_name }}</option>
 	                            {% endfor %}
diff --git a/ipynbsrv/web/templates/web/images/modal_create.html b/ipynbsrv/web/templates/web/images/modal_create.html
index 2e0b5e9..c321165 100644
--- a/ipynbsrv/web/templates/web/images/modal_create.html
+++ b/ipynbsrv/web/templates/web/images/modal_create.html
@@ -14,7 +14,7 @@ <h4 class="modal-title">New image</h4>
                         <label for="ct_id">Base container</label>
                         <div class="select">
 	                        <select name="ct_id" class="form-control enableCaseInsensitiveFiltering" required>
-	                            <option>None</option>
+	                            <option value="" selected>None</option>
 	                            {% for ct in containers %}
 	                                <option value="{{ ct.id }}"{% if ct == selected %} selected{% endif %}>{{ ct.name }}</option>
 	                            {% endfor %}
diff --git a/ipynbsrv/web/templates/web/shares/modal_addgroups.html b/ipynbsrv/web/templates/web/shares/modal_addgroups.html
index 43e4cd3..2b4a39e 100644
--- a/ipynbsrv/web/templates/web/shares/modal_addgroups.html
+++ b/ipynbsrv/web/templates/web/shares/modal_addgroups.html
@@ -15,7 +15,7 @@ <h4 class="modal-title">Add share user</h4>
                     <div class="form-group">
                         <label for="access_groups">Groups</label>
                         <div class="select">
-                            <select class="enableMultiselectCaseInsensitiveFiltering" multiple="multiple" name="access_groups">
+                            <select class="enableMultiselectCaseInsensitiveFiltering" multiple="multiple" name="access_groups" required>
                                 {% for group in groups %}
                                 {% if group.id not in share.access_group_ids and not group.is_single_user_group %}
                                         <option value="{{ group.id }}">{{ group.name }}</option>
diff --git a/ipynbsrv/web/templates/web/shares/modal_addusers.html b/ipynbsrv/web/templates/web/shares/modal_addusers.html
index 2322004..07e8fc8 100644
--- a/ipynbsrv/web/templates/web/shares/modal_addusers.html
+++ b/ipynbsrv/web/templates/web/shares/modal_addusers.html
@@ -15,7 +15,7 @@ <h4 class="modal-title">Add share user</h4>
                 <div class="form-group">
                         <label for="access_groups">Users</label>
                         <div class="select">
-                            <select class="enableMultiselectCaseInsensitiveFiltering" multiple="multiple" name="access_groups">
+                            <select class="enableMultiselectCaseInsensitiveFiltering" multiple="multiple" name="access_groups" required>
                                 {% for user in users %}
                                 {% if user.backend_user.collab_group %}
                                     {% if user.backend_user.collab_group.id not in share.access_group_ids and user != request.user %}
diff --git a/ipynbsrv/web/views/collaborationgroups.py b/ipynbsrv/web/views/collaborationgroups.py
index 8848f82..522cd75 100644
--- a/ipynbsrv/web/views/collaborationgroups.py
+++ b/ipynbsrv/web/views/collaborationgroups.py
@@ -86,7 +86,7 @@ def delete(request):
     if request.method != "POST":
         messages.error(request, "Invalid request method.")
         return redirect('groups')
-    if 'group_id' not in request.POST:
+    if 'group_id' not in request.POST  or not request.POST.get('group_id').isdigit():
         messages.error(request, "Invalid POST request.")
         return redirect('shares')
 
@@ -112,7 +112,8 @@ def add_admin(request):
     if request.method != "POST":
         messages.error(request, "Invalid request method.")
         return redirect('shares')
-    if 'group_id' not in request.POST or 'user_id' not in request.POST:
+    if 'group_id' not in request.POST  or not request.POST.get('group_id').isdigit() \
+        or 'user_id' not in request.POST  or not request.POST.get('user_id').isdigit():
         messages.error(request, "Invalid POST request.")
         return redirect('shares')
 
@@ -149,7 +150,8 @@ def remove_admin(request):
     if request.method != "POST":
         messages.error(request, "Invalid request method.")
         return redirect('shares')
-    if 'group_id' not in request.POST or 'user_id' not in request.POST:
+    if 'group_id' not in request.POST  or not request.POST.get('group_id').isdigit() \
+        or 'user_id' not in request.POST  or not request.POST.get('user_id').isdigit():
         messages.error(request, "Invalid POST request.")
         return redirect('shares')
 
@@ -216,7 +218,8 @@ def remove_member(request):
     if request.method != "POST":
         messages.error(request, "Invalid request method.")
         return redirect('groups')
-    if 'group_id' not in request.POST or 'user_id' not in request.POST:
+    if 'group_id' not in request.POST or not request.POST.get('group_id').isdigit() \
+         or 'user_id' not in request.POST  or not request.POST.get('user_id').isdigit():
         messages.error(request, "Invalid POST request.")
         return redirect('groups')
 
@@ -255,7 +258,7 @@ def leave(request):
     if request.method != "POST":
         messages.error(request, "Invalid request method.")
         return redirect('groups')
-    if 'group_id' not in request.POST:
+    if 'group_id' not in request.POST or not request.POST.get('group_id').isdigit():
         messages.error(request, "Invalid POST request.")
         return redirect('groups')
 
@@ -284,7 +287,7 @@ def join(request):
     if request.method != "POST":
         messages.error(request, "Invalid request method.")
         return redirect('shares')
-    if 'group_id' not in request.POST:
+    if 'group_id' not in request.POST or not request.POST.get('group_id').isdigit():
         messages.error(request, "Invalid POST request.")
         return redirect('groups')
 
diff --git a/ipynbsrv/web/views/containers.py b/ipynbsrv/web/views/containers.py
index 606d3b8..4c7fa63 100644
--- a/ipynbsrv/web/views/containers.py
+++ b/ipynbsrv/web/views/containers.py
@@ -17,7 +17,8 @@ def create_snapshot(request):
     if request.method != "POST":
         messages.error(request, "Invalid request method.")
         return redirect('containers')
-    if 'ct_id' not in request.POST or 'name' not in request.POST:
+    if 'ct_id' not in request.POST  or not request.POST.get('ct_id').isdigit() \
+        or 'name' not in request.POST:
         messages.error(request, "Invalid POST request.")
         return redirect('containers')
 
@@ -49,7 +50,7 @@ def clone(request):
     if request.method != "POST":
         messages.error(request, "Invalid request method.")
         return redirect('containers')
-    if 'id' not in request.POST:
+    if 'id' not in request.POST or not request.POST.get('id').isdigit():
         messages.error(request, "Invalid POST request.")
         return redirect('containers')
 
@@ -79,7 +80,8 @@ def commit(request):
     if request.method != "POST":
         messages.error(request, "Invalid request method.")
         return redirect('images')
-    if 'ct_id' not in request.POST or 'img_name' not in request.POST or 'description' not in request.POST:
+    if 'ct_id' not in request.POST or not request.POST.get('ct_id').isdigit() \
+        or 'img_name' not in request.POST or 'description' not in request.POST:
         messages.error(request, "Invalid POST request.")
         return redirect('images')
 
@@ -115,10 +117,12 @@ def create(request):
     """
     Todo: write doc.
     """
+    print(request.POST)
     if request.method != "POST":
         messages.error(request, "Invalid request method.")
         return redirect('images')
-    if 'name' not in request.POST or 'description' not in request.POST or 'image_id' not in request.POST:
+    if 'name' not in request.POST or 'description' not in request.POST \
+        or 'image_id' not in request.POST or not request.POST.get('image_id').isdigit():
         messages.error(request, "Invalid POST request.")
         return redirect('images')
 
@@ -155,7 +159,7 @@ def delete(request):
     if request.method != "POST":
         messages.error(request, "Invalid request method.")
         return redirect('containers')
-    if 'id' not in request.POST:
+    if 'id' not in request.POST or not request.POST.get('id').isdigit():
         messages.error(request, "Invalid POST request.")
         return redirect('containers')
 
@@ -207,7 +211,7 @@ def restart(request):
     if request.method != "POST":
         messages.error(request, "Invalid request method.")
         return redirect('containers')
-    if 'id' not in request.POST:
+    if 'id' not in request.POST or not request.POST.get('id').isdigit():
         messages.error(request, "Invalid POST request.")
         return redirect('containers')
 
@@ -240,7 +244,7 @@ def start(request):
     if request.method != "POST":
         messages.error(request, "Invalid request method.")
         return redirect('containers')
-    if 'id' not in request.POST:
+    if 'id' not in request.POST or not request.POST.get('id').isdigit():
         messages.error(request, "Invalid POST request.")
         return redirect('containers')
 
@@ -273,7 +277,7 @@ def stop(request):
     if request.method != "POST":
         messages.error(request, "Invalid request method.")
         return redirect('containers')
-    if 'id' not in request.POST:
+    if 'id' not in request.POST or not request.POST.get('id').isdigit():
         messages.error(request, "Invalid POST request.")
         return redirect('containers')
 
@@ -306,7 +310,7 @@ def suspend(request):
     if request.method != "POST":
         messages.error(request, "Invalid request method.")
         return redirect('containers')
-    if 'id' not in request.POST:
+    if 'id' not in request.POST or not request.POST.get('id').isdigit():
         messages.error(request, "Invalid POST request.")
         return redirect('containers')
 
@@ -339,7 +343,7 @@ def resume(request):
     if request.method != "POST":
         messages.error(request, "Invalid request method.")
         return redirect('containers')
-    if 'id' not in request.POST:
+    if 'id' not in request.POST or not request.POST.get('id').isdigit():
         messages.error(request, "Invalid POST request.")
         return redirect('containers')
 
@@ -374,7 +378,7 @@ def restore_snapshot(request):
     if request.method != "POST":
         messages.error(request, "Invalid request method.")
         return redirect('containers')
-    if 'id' not in request.POST:
+    if 'id' not in request.POST or not request.POST.get('id').isdigit():
         messages.error(request, "Invalid POST request.")
         return redirect('containers')
 
@@ -388,7 +392,7 @@ def restore_snapshot(request):
         # restore snapshot
         try:
             client.containers.snapshots(id).restore.post()
-            messages.success(request, "Sucessfully restored snapshot `{}`.".format(snapshot.name)
+            messages.success(request, "Sucessfully restored snapshot `{}`.".format(snapshot.name))
         except Exception as e:
                 messages.error(request, api_error_message(e, ""))
     else:
@@ -406,7 +410,8 @@ def delete_snapshot(request):
     if request.method != "POST":
         messages.error(request, "Invalid request method.")
         return redirect('containers')
-    if 'id' not in request.POST or 'ct_id' not in request.POST:
+    if 'id' not in request.POST or not request.POST.get('id').isdgit() \
+        or 'ct_id' not in request.POST or not request.get('ct_id').isdgit():
         messages.error(request, "Invalid POST request.")
         return redirect('containers')
 
diff --git a/ipynbsrv/web/views/images.py b/ipynbsrv/web/views/images.py
index f6441fe..d7a6a97 100644
--- a/ipynbsrv/web/views/images.py
+++ b/ipynbsrv/web/views/images.py
@@ -12,7 +12,7 @@ def delete(request):
     if request.method != "POST":
         messages.error(request, "Invalid request method.")
         return redirect('images')
-    if 'id' not in request.POST:
+    if 'id' not in request.POST or not request.POST.get('id').isdigit():
         messages.error(request, "Invalid POST request.")
         return redirect('images')
 
diff --git a/ipynbsrv/web/views/notifications.py b/ipynbsrv/web/views/notifications.py
index 9057edf..b1e2a69 100644
--- a/ipynbsrv/web/views/notifications.py
+++ b/ipynbsrv/web/views/notifications.py
@@ -46,7 +46,8 @@ def create(request):
         messages.error(request, "Invalid request method.")
         return redirect('notifications')
     # Todo: validate POST params: receiver_group, msg, type, rel objs
-    if 'receiver_groups' not in request.POST or 'message' not in request.POST or 'notification_type' not in request.POST:
+    if 'receiver_groups' not in request.POST or 'message' not in request.POST \
+        or 'notification_type' not in request.POST:
         messages.error(request, "Invalid POST request.")
         return redirect('notifications')
 
@@ -77,8 +78,7 @@ def mark_as_read(request):
     if request.method != "POST":
         messages.error(request, "Invalid request method.")
         return redirect('notifications')
-    # Todo: validate POST params: receiver_group, msg, type, rel objs
-    if 'id' not in request.POST:
+    if 'id' not in request.POST  or not request.POST.get('id').isdigit():
         messages.error(request, "Invalid POST request.")
         return redirect('notifications')
 
diff --git a/ipynbsrv/web/views/shares.py b/ipynbsrv/web/views/shares.py
index f791694..fd1ca46 100644
--- a/ipynbsrv/web/views/shares.py
+++ b/ipynbsrv/web/views/shares.py
@@ -91,7 +91,7 @@ def share_add_access_groups(request):
     if request.method != "POST":
         messages.error(request, "Invalid request method.")
         return redirect('shares')
-    if 'id' not in request.POST or 'access_groups' not in request.POST:
+    if 'id' not in request.POST  or not request.POST.get('id').isdigit() or 'access_groups' not in request.POST:
         messages.error(request, "Invalid POST request.")
         return redirect('shares')
 
@@ -149,7 +149,7 @@ def delete(request):
     if request.method != "POST":
         messages.error(request, "Invalid request method.")
         return redirect('shares')
-    if 'share_id' not in request.POST:
+    if 'share_id' not in request.POST or not request.POST.get('share_id').isdigit():
         messages.error(request, "Invalid POST request.")
         return redirect('shares')
 
@@ -178,7 +178,7 @@ def leave(request):
     if request.method != "POST":
         messages.error(request, "Invalid request method.")
         return redirect('shares')
-    if 'id' not in request.POST:
+    if 'id' not in request.POST or not request.POST.get('id').isdigit():
         messages.error(request, "Invalid POST request.")
         return redirect('shares')