diff --git a/backend/account_v2/serializer.py b/backend/account_v2/serializer.py
index 4011cf4d5a..e189b4efe1 100644
--- a/backend/account_v2/serializer.py
+++ b/backend/account_v2/serializer.py
@@ -1,6 +1,7 @@
 import re
 
 from rest_framework import serializers
+from utils.input_sanitizer import validate_name_field
 
 from account_v2.models import Organization, User
 
@@ -10,6 +11,12 @@ class OrganizationSignupSerializer(serializers.Serializer):
     display_name = serializers.CharField(required=True, max_length=150)
     organization_id = serializers.CharField(required=True, max_length=30)
 
+    def validate_name(self, value: str) -> str:
+        return validate_name_field(value, field_name="Organization name")
+
+    def validate_display_name(self, value: str) -> str:
+        return validate_name_field(value, field_name="Display name")
+
     def validate_organization_id(self, value):  # type: ignore
         if not re.match(r"^[a-z0-9_-]+$", value):
             raise serializers.ValidationError(
diff --git a/backend/adapter_processor_v2/serializers.py b/backend/adapter_processor_v2/serializers.py
index 1d931f1266..3550c4003f 100644
--- a/backend/adapter_processor_v2/serializers.py
+++ b/backend/adapter_processor_v2/serializers.py
@@ -6,6 +6,7 @@
 from django.conf import settings
 from rest_framework import serializers
 from rest_framework.serializers import ModelSerializer
+from utils.input_sanitizer import validate_name_field, validate_no_html_tags
 
 from adapter_processor_v2.adapter_processor import AdapterProcessor
 from adapter_processor_v2.constants import AdapterKeys
@@ -28,6 +29,20 @@ class Meta:
         model = AdapterInstance
         fields = "__all__"
 
+    def validate(self, data):
+        data = super().validate(data)
+        adapter_name = data.get("adapter_name")
+        if adapter_name is not None:
+            data["adapter_name"] = validate_name_field(
+                adapter_name, field_name="Adapter name"
+            )
+        description = data.get("description")
+        if description is not None:
+            data["description"] = validate_no_html_tags(
+                description, field_name="Description"
+            )
+        return data
+
 
 class DefaultAdapterSerializer(serializers.Serializer):
     llm_default = serializers.CharField(max_length=FLC.UUID_LENGTH, required=False)
diff --git a/backend/api_v2/serializers.py b/backend/api_v2/serializers.py
index 5a2068fd93..4f81ef7c49 100644
--- a/backend/api_v2/serializers.py
+++ b/backend/api_v2/serializers.py
@@ -22,6 +22,7 @@
     ValidationError,
 )
 from tags.serializers import TagParamsSerializer
+from utils.input_sanitizer import validate_name_field, validate_no_html_tags
 from utils.serializer.integrity_error_mixin import IntegrityErrorMixin
 from workflow_manager.endpoint_v2.models import WorkflowEndpoint
 from workflow_manager.workflow_v2.exceptions import ExecutionDoesNotExistError
@@ -62,6 +63,14 @@ def validate_api_name(self, value: str) -> str:
         api_name_validator(value)
         return value
 
+    def validate_display_name(self, value: str) -> str:
+        return validate_name_field(value, field_name="Display name")
+
+    def validate_description(self, value: str) -> str:
+        if value is None:
+            return value
+        return validate_no_html_tags(value, field_name="Description")
+
     def validate_workflow(self, workflow):
         """Validate that the workflow has properly configured source and destination endpoints."""
         # Get all endpoints for this workflow with related data
diff --git a/backend/backend/settings/base.py b/backend/backend/settings/base.py
index 97e5be789d..64c393d735 100644
--- a/backend/backend/settings/base.py
+++ b/backend/backend/settings/base.py
@@ -418,6 +418,7 @@ def filter(self, record):
     "social_django.middleware.SocialAuthExceptionMiddleware",
     "middleware.remove_allow_header.RemoveAllowHeaderMiddleware",
     "middleware.cache_control.CacheControlMiddleware",
+    "middleware.content_security_policy.ContentSecurityPolicyMiddleware",
 ]
 
 TENANT_SUBFOLDER_PREFIX = f"{PATH_PREFIX}/unstract"
diff --git a/backend/connector_v2/serializers.py b/backend/connector_v2/serializers.py
index 45d5c07562..5517bc5257 100644
--- a/backend/connector_v2/serializers.py
+++ b/backend/connector_v2/serializers.py
@@ -9,6 +9,7 @@
 from connector_processor.exceptions import OAuthTimeOut
 from rest_framework.serializers import CharField, SerializerMethodField
 from utils.fields import EncryptedBinaryFieldSerializer
+from utils.input_sanitizer import validate_name_field
 
 from backend.serializers import AuditSerializer
 from connector_v2.constants import ConnectorInstanceKey as CIKey
@@ -28,6 +29,9 @@ class Meta:
         model = ConnectorInstance
         fields = "__all__"
 
+    def validate_connector_name(self, value: str) -> str:
+        return validate_name_field(value, field_name="Connector name")
+
     def save(self, **kwargs):  # type: ignore
         user = self.context.get("request").user or None
         connector_id: str = kwargs[CIKey.CONNECTOR_ID]
diff --git a/backend/middleware/content_security_policy.py b/backend/middleware/content_security_policy.py
new file mode 100644
index 0000000000..caa142ba43
--- /dev/null
+++ b/backend/middleware/content_security_policy.py
@@ -0,0 +1,31 @@
+from django.http import HttpRequest, HttpResponse
+from django.utils.deprecation import MiddlewareMixin
+
+
+class ContentSecurityPolicyMiddleware(MiddlewareMixin):
+    """Middleware to add Content-Security-Policy header to all responses.
+
+    Since this is a JSON API backend, the policy is restrictive by default:
+    only 'self' is allowed for all directives, and no inline scripts or styles
+    are permitted. This prevents any injected content from being executed if a
+    response is ever rendered in a browser context.
+    """
+
+    def process_response(
+        self, request: HttpRequest, response: HttpResponse
+    ) -> HttpResponse:
+        response.setdefault(
+            "Content-Security-Policy",
+            (
+                "default-src 'self'; "
+                "script-src 'self'; "
+                "style-src 'self'; "
+                "img-src 'self'; "
+                "font-src 'self'; "
+                "connect-src 'self'; "
+                "frame-ancestors 'none'; "
+                "base-uri 'self'; "
+                "form-action 'self'"
+            ),
+        )
+        return response
diff --git a/backend/notification_v2/serializers.py b/backend/notification_v2/serializers.py
index cd82fed8a6..115487c481 100644
--- a/backend/notification_v2/serializers.py
+++ b/backend/notification_v2/serializers.py
@@ -1,4 +1,5 @@
 from rest_framework import serializers
+from utils.input_sanitizer import validate_name_field
 
 from .enums import AuthorizationType, NotificationType, PlatformType
 from .models import Notification
@@ -109,6 +110,8 @@ def validate_name(self, value):
         """Check uniqueness of the name with respect to either 'api' or
         'pipeline'.
         """
+        value = validate_name_field(value, field_name="Notification name")
+
         api = self.initial_data.get("api", getattr(self.instance, "api", None))
         pipeline = self.initial_data.get(
             "pipeline", getattr(self.instance, "pipeline", None)
diff --git a/backend/prompt_studio/prompt_studio_core_v2/serializers.py b/backend/prompt_studio/prompt_studio_core_v2/serializers.py
index 9a90fa3583..fd13e9b289 100644
--- a/backend/prompt_studio/prompt_studio_core_v2/serializers.py
+++ b/backend/prompt_studio/prompt_studio_core_v2/serializers.py
@@ -8,6 +8,7 @@
 from rest_framework import serializers
 from rest_framework.exceptions import ValidationError
 from utils.FileValidator import FileValidator
+from utils.input_sanitizer import validate_name_field, validate_no_html_tags
 from utils.serializer.integrity_error_mixin import IntegrityErrorMixin
 
 from backend.serializers import AuditSerializer
@@ -51,6 +52,12 @@ class Meta:
         }
     }
 
+    def validate_tool_name(self, value: str) -> str:
+        return validate_name_field(value, field_name="Tool name")
+
+    def validate_description(self, value: str) -> str:
+        return validate_no_html_tags(value, field_name="Description")
+
     def validate_summarize_llm_adapter(self, value):
         """Validate that the adapter type is LLM and is accessible to the user."""
         if value is None:
diff --git a/backend/utils/input_sanitizer.py b/backend/utils/input_sanitizer.py
new file mode 100644
index 0000000000..bb71a2559f
--- /dev/null
+++ b/backend/utils/input_sanitizer.py
@@ -0,0 +1,29 @@
+import re
+
+from rest_framework.serializers import ValidationError
+
+# Pattern to detect HTML/script tags
+HTML_TAG_PATTERN = re.compile(r"<[^>]*>")
+# Pattern to detect javascript: protocol
+JS_PROTOCOL_PATTERN = re.compile(r"javascript\s*:", re.IGNORECASE)
+# Pattern to detect event handlers (onclick, onerror, etc.)
+EVENT_HANDLER_PATTERN = re.compile(r"(?:^|\s)on\w+\s*=", re.IGNORECASE)
+
+
+def validate_no_html_tags(value: str, field_name: str = "This field") -> str:
+    """Reject values containing HTML/script tags."""
+    if HTML_TAG_PATTERN.search(value):
+        raise ValidationError(f"{field_name} must not contain HTML or script tags.")
+    if JS_PROTOCOL_PATTERN.search(value):
+        raise ValidationError(f"{field_name} must not contain JavaScript protocols.")
+    if EVENT_HANDLER_PATTERN.search(value):
+        raise ValidationError(f"{field_name} must not contain event handler attributes.")
+    return value
+
+
+def validate_name_field(value: str, field_name: str = "This field") -> str:
+    """Validate name/identifier fields - no HTML tags, strip whitespace."""
+    value = value.strip()
+    if not value:
+        raise ValidationError(f"{field_name} must not be empty.")
+    return validate_no_html_tags(value, field_name)
diff --git a/backend/utils/tests/__init__.py b/backend/utils/tests/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/backend/utils/tests/test_input_sanitizer.py b/backend/utils/tests/test_input_sanitizer.py
new file mode 100644
index 0000000000..08353af658
--- /dev/null
+++ b/backend/utils/tests/test_input_sanitizer.py
@@ -0,0 +1,97 @@
+import pytest
+from rest_framework.serializers import ValidationError
+
+from utils.input_sanitizer import validate_name_field, validate_no_html_tags
+
+
+class TestValidateNoHtmlTags:
+    def test_clean_input_passes(self):
+        assert validate_no_html_tags("Hello World") == "Hello World"
+
+    def test_allows_normal_special_chars(self):
+        assert (
+            validate_no_html_tags("My workflow (v2), test - final")
+            == "My workflow (v2), test - final"
+        )
+
+    def test_allows_numbers_and_punctuation(self):
+        assert validate_no_html_tags("Test 123 & more!") == "Test 123 & more!"
+
+    def test_rejects_script_tag(self):
+        with pytest.raises(ValidationError, match="must not contain HTML or script tags"):
+            validate_no_html_tags("<script>alert(1)</script>")
+
+    def test_rejects_img_tag(self):
+        with pytest.raises(ValidationError, match="must not contain HTML or script tags"):
+            validate_no_html_tags('<img src=x onerror=alert(1)>')
+
+    def test_rejects_div_tag(self):
+        with pytest.raises(ValidationError, match="must not contain HTML or script tags"):
+            validate_no_html_tags("<div>content</div>")
+
+    def test_rejects_self_closing_tag(self):
+        with pytest.raises(ValidationError, match="must not contain HTML or script tags"):
+            validate_no_html_tags("<br/>")
+
+    def test_rejects_javascript_protocol(self):
+        with pytest.raises(ValidationError, match="must not contain JavaScript protocols"):
+            validate_no_html_tags("javascript:alert(1)")
+
+    def test_rejects_javascript_protocol_with_spaces(self):
+        with pytest.raises(ValidationError, match="must not contain JavaScript protocols"):
+            validate_no_html_tags("javascript :alert(1)")
+
+    def test_rejects_javascript_protocol_case_insensitive(self):
+        with pytest.raises(ValidationError, match="must not contain JavaScript protocols"):
+            validate_no_html_tags("JAVASCRIPT:alert(1)")
+
+    def test_rejects_event_handler(self):
+        with pytest.raises(
+            ValidationError, match="must not contain event handler attributes"
+        ):
+            validate_no_html_tags("onclick=alert(1)")
+
+    def test_rejects_event_handler_with_spaces(self):
+        with pytest.raises(
+            ValidationError, match="must not contain event handler attributes"
+        ):
+            validate_no_html_tags("onerror =alert(1)")
+
+    def test_rejects_event_handler_case_insensitive(self):
+        with pytest.raises(
+            ValidationError, match="must not contain event handler attributes"
+        ):
+            validate_no_html_tags("ONLOAD=alert(1)")
+
+    def test_custom_field_name_in_error(self):
+        with pytest.raises(ValidationError, match="Workflow name"):
+            validate_no_html_tags("<script>", field_name="Workflow name")
+
+
+class TestValidateNameField:
+    def test_clean_name_passes(self):
+        assert validate_name_field("My Workflow") == "My Workflow"
+
+    def test_strips_whitespace(self):
+        assert validate_name_field("  hello  ") == "hello"
+
+    def test_rejects_empty_after_strip(self):
+        with pytest.raises(ValidationError, match="must not be empty"):
+            validate_name_field("   ")
+
+    def test_rejects_html_tags(self):
+        with pytest.raises(ValidationError, match="must not contain HTML or script tags"):
+            validate_name_field("<script>alert(1)</script>")
+
+    def test_allows_hyphens_and_underscores(self):
+        assert validate_name_field("my-workflow_v2") == "my-workflow_v2"
+
+    def test_allows_periods(self):
+        assert validate_name_field("config.v2") == "config.v2"
+
+    def test_allows_parentheses_and_commas(self):
+        assert validate_name_field("Test (v2), final") == "Test (v2), final"
+
+    def test_custom_field_name_in_error(self):
+        with pytest.raises(ValidationError, match="Tool name"):
+            validate_name_field("   ", field_name="Tool name")
diff --git a/backend/workflow_manager/workflow_v2/serializers.py b/backend/workflow_manager/workflow_v2/serializers.py
index 6442d1e1fa..108aadd13f 100644
--- a/backend/workflow_manager/workflow_v2/serializers.py
+++ b/backend/workflow_manager/workflow_v2/serializers.py
@@ -14,6 +14,7 @@
 )
 from tool_instance_v2.serializers import ToolInstanceSerializer
 from tool_instance_v2.tool_instance_helper import ToolInstanceHelper
+from utils.input_sanitizer import validate_name_field, validate_no_html_tags
 from utils.serializer.integrity_error_mixin import IntegrityErrorMixin
 
 from backend.constants import RequestKey
@@ -46,6 +47,12 @@ class Meta:
         }
     }
 
+    def validate_workflow_name(self, value: str) -> str:
+        return validate_name_field(value, field_name="Workflow name")
+
+    def validate_description(self, value: str) -> str:
+        return validate_no_html_tags(value, field_name="Description")
+
     def to_representation(self, instance: Workflow) -> dict[str, str]:
         representation: dict[str, str] = super().to_representation(instance)
         representation[WorkflowKey.WF_NAME] = instance.workflow_name
diff --git a/frontend/nginx.conf b/frontend/nginx.conf
index f3eef19532..27f1bd04ac 100644
--- a/frontend/nginx.conf
+++ b/frontend/nginx.conf
@@ -47,6 +47,27 @@ http {
         add_header X-Frame-Options "SAMEORIGIN" always;
         add_header Referrer-Policy "strict-origin-when-cross-origin" always;
 
+        # Content Security Policy
+        # - 'unsafe-inline' in script-src: required for runtime-config.js injected at container start
+        # - 'unsafe-inline' in style-src: required by Ant Design CSS-in-JS
+        # - cdn.jsdelivr.net: Monaco Editor loads from this CDN
+        # - unpkg.com: PDF.js worker
+        # - PostHog, GTM, reCAPTCHA, Stripe, Product Fruits: third-party services
+        add_header Content-Security-Policy
+            "default-src 'self'; "
+            "script-src 'self' 'unsafe-inline' https://cdn.jsdelivr.net https://unpkg.com https://eu.i.posthog.com https://eu-assets.i.posthog.com https://www.googletagmanager.com https://www.google.com/recaptcha/ https://www.gstatic.com/recaptcha/ https://js.stripe.com https://app.productfruits.com; "
+            "style-src 'self' 'unsafe-inline'; "
+            "img-src 'self' data: blob: https:; "
+            "font-src 'self' data:; "
+            "connect-src 'self' ws: wss: https://eu.i.posthog.com https://eu-assets.i.posthog.com https://www.google-analytics.com https://api.stripe.com https://app.productfruits.com; "
+            "frame-src 'self' https://www.google.com/recaptcha/ https://recaptcha.google.com https://js.stripe.com https://hooks.stripe.com; "
+            "worker-src 'self' blob: https://unpkg.com https://cdn.jsdelivr.net; "
+            "object-src 'none'; "
+            "base-uri 'self'; "
+            "form-action 'self' https://checkout.stripe.com; "
+            "frame-ancestors 'self'"
+            always;
+
         # Disable TRACE and TRACK methods
         if ($request_method ~ ^(TRACE|TRACK)$) {
             return 405;