diff --git a/CHANGELOG.md b/CHANGELOG.md
index fe263bf..e763d5e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,16 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [1.8.4] - 2026-04-09
+
+### Security
+- Fix Remote Code Execution (RCE) via Jinja2 Server-Side Template Injection in transformations (CVSS 9.2 Critical)
+- Fix arbitrary file write via path traversal in file upload (CVSS 7.0 High)
+- Fix arbitrary file read via Local File Inclusion in source creation (CVSS 8.2 High)
+
+### Dependencies
+- Bump ai-prompter to >=0.4.0 (uses Jinja2 SandboxedEnvironment to prevent SSTI)
+
 ## [1.8.3] - 2026-04-07
 
 ### Security
diff --git a/api/routers/sources.py b/api/routers/sources.py
index 38e75a3..e6d6eff 100644
--- a/api/routers/sources.py
+++ b/api/routers/sources.py
@@ -43,21 +43,30 @@ def generate_unique_filename(original_filename: str, upload_folder: str) -> str:
     file_path = Path(upload_folder)
     file_path.mkdir(parents=True, exist_ok=True)
 
+    # Strip directory components to prevent path traversal
+    safe_filename = os.path.basename(original_filename)
+    if not safe_filename:
+        raise ValueError("Invalid filename")
+
     # Split filename and extension
-    stem = Path(original_filename).stem
-    suffix = Path(original_filename).suffix
+    stem = Path(safe_filename).stem
+    suffix = Path(safe_filename).suffix
 
     # Check if file exists and generate unique name
     counter = 0
     while True:
         if counter == 0:
-            new_filename = original_filename
+            new_filename = safe_filename
         else:
             new_filename = f"{stem} ({counter}){suffix}"
 
         full_path = file_path / new_filename
-        if not full_path.exists():
-            return str(full_path)
+        # Verify resolved path stays within upload folder
+        resolved = full_path.resolve()
+        if not str(resolved).startswith(str(file_path.resolve())):
+            raise ValueError("Invalid filename: path traversal detected")
+        if not resolved.exists():
+            return str(resolved)
         counter += 1
 
 
@@ -325,6 +334,14 @@ async def create_source(
                     status_code=400,
                     detail="File upload or file_path is required for upload type",
                 )
+            # Validate file_path is within the uploads directory to prevent LFI
+            uploads_resolved = Path(UPLOADS_FOLDER).resolve()
+            file_resolved = Path(final_file_path).resolve()
+            if not str(file_resolved).startswith(str(uploads_resolved)):
+                raise HTTPException(
+                    status_code=400,
+                    detail="Invalid file path: must be within the uploads directory",
+                )
             content_state["file_path"] = final_file_path
             content_state["delete_source"] = source_data.delete_source
         elif source_data.type == "text":
diff --git a/pyproject.toml b/pyproject.toml
index f526a90..8814dc2 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [project]
 name = "open-notebook"
-version = "1.8.3"
+version = "1.8.4"
 description = "An open source implementation of a research assistant, inspired by Google Notebook LM"
 authors = [
     {name = "Luis Novo", email = "lfnovo@gmail.com"}
@@ -33,7 +33,7 @@ dependencies = [
     "python-dotenv>=1.0.1",
     "httpx[socks]>=0.27.0",
     "content-core>=1.14.1,<2",
-    "ai-prompter>=0.3,<1",
+    "ai-prompter>=0.4,<1",
     "esperanto>=2.20.0,<3",
     "surrealdb>=1.0.4",
     "podcast-creator>=0.12.0,<1",
diff --git a/tests/test_sources_api.py b/tests/test_sources_api.py
index 06db1c4..f33cf6b 100644
--- a/tests/test_sources_api.py
+++ b/tests/test_sources_api.py
@@ -1,10 +1,12 @@
 """Tests for the sources API endpoint."""
 
+import os
 from unittest.mock import AsyncMock, MagicMock, patch
 
 import pytest
 from fastapi.testclient import TestClient
 
+from open_notebook.config import UPLOADS_FOLDER
 from open_notebook.domain.notebook import Source
 
 
@@ -71,7 +73,7 @@ class TestAsyncSourceAssetPersistence:
     ):
         """POST /sources with type=upload and async_processing=true persists Asset(file_path=...)."""
         mock_nb_get.return_value = MagicMock()
-        mock_upload.return_value = "/tmp/uploads/video.mp4"
+        mock_upload.return_value = os.path.join(os.path.abspath(UPLOADS_FOLDER), "video.mp4")
         mock_submit.return_value = "command:123"
 
         saved_sources = []
@@ -97,7 +99,7 @@ class TestAsyncSourceAssetPersistence:
 
         source = saved_sources[0]
         assert source.asset is not None
-        assert source.asset.file_path == "/tmp/uploads/video.mp4"
+        assert source.asset.file_path == os.path.join(os.path.abspath(UPLOADS_FOLDER), "video.mp4")
         assert source.asset.url is None
 
     @pytest.mark.asyncio
diff --git a/uv.lock b/uv.lock
index 10608e2..a2235db 100644
--- a/uv.lock
+++ b/uv.lock
@@ -9,16 +9,16 @@ resolution-markers = [
 
 [[package]]
 name = "ai-prompter"
-version = "0.3.1"
+version = "0.4.0"
 source = { registry = "https://pypi.org/simple" }
 dependencies = [
     { name = "jinja2" },
     { name = "pip" },
     { name = "pydantic" },
 ]
-sdist = { url = "https://files.pythonhosted.org/packages/52/88/cadc58aac8bbb599d8c6d25f2cd357e938ddabe3756b1eed68e8860eed22/ai_prompter-0.3.1.tar.gz", hash = "sha256:cec7fddac5edf7d836c13fe77613e16b12b23aea625133846d11ae22455ed397", size = 84837, upload-time = "2025-06-20T19:31:36.879Z" }
+sdist = { url = "https://files.pythonhosted.org/packages/46/a6/0703f5de846d4ccdc6cdfc7e44473f2722125e95316a50d44303b80edbe6/ai_prompter-0.4.0.tar.gz", hash = "sha256:63a8f2c19f13c0313ee7cef58f07cc00e948546c83c335c42737e076ae764385", size = 86469, upload-time = "2026-04-09T14:54:32.243Z" }
 wheels = [
-    { url = "https://files.pythonhosted.org/packages/7d/f6/490bf534d6b04755998142ec7412b78e7466dc6d9a3f31e90541506b7971/ai_prompter-0.3.1-py3-none-any.whl", hash = "sha256:ec26566f7f246f511325e1c0f260970963a6e49fb19ed0767152d30b82cd2b79", size = 13386, upload-time = "2025-06-20T19:31:34.952Z" },
+    { url = "https://files.pythonhosted.org/packages/bd/c3/881c31c26a7a131ed9e1a2c1c3838b5bb95e3822ac88c68fcda7738c5395/ai_prompter-0.4.0-py3-none-any.whl", hash = "sha256:230662484a27de34e8677ebe20a8220c78f8b605cb68005253c5dbf3e5cc254e", size = 13777, upload-time = "2026-04-09T14:54:33.017Z" },
 ]
 
 [[package]]
@@ -2126,7 +2126,7 @@ dev = [
 
 [package.metadata]
 requires-dist = [
-    { name = "ai-prompter", specifier = ">=0.3,<1" },
+    { name = "ai-prompter", specifier = ">=0.4,<1" },
     { name = "babel", specifier = ">=2.18.0" },
     { name = "content-core", specifier = ">=1.14.1,<2" },
     { name = "esperanto", specifier = ">=2.20.0,<3" },