diff --git a/README.md b/README.md
index de7aca1..1022962 100644
--- a/README.md
+++ b/README.md
@@ -19,6 +19,14 @@ cargo install hexo
 
 Use `hexo -h` to get complete CLI manual.
 
+### Arguments
+
+- `log-level`
+  : Set log level, possible values: `debug`, `info`, `warn`, `error`, `none`. Default: `info`.
+
+- `safe`
+  : Enable safe mode, will disable unsafe functions like `cmd` and `eval`. Default: `false`
+
 ### Commands
 
 #### build
@@ -37,7 +45,6 @@ Takes `source` file in hexo format and compiles it to binary file `output`. Will
 hexo watch --source <path to source> --output <path to output>
 ```
 
-
 ## Syntax
 
 ### Emitter
@@ -142,4 +149,6 @@ Not currently, but this is planned for future releases.
 ### Isn't `cmd` function highly unsafe?
 
 Yes, safety is no goal of Hexo, please don't run untrusted code with it.
-Safe mode might be implemented in the future is there is enough demand for it.
+
+You can use safe mode to disable `cmd` and `eval` functions.
+Please add `--safe` flag before command to enable it.
\ No newline at end of file
diff --git a/src/compiler/compiler_context.rs b/src/compiler/compiler_context.rs
index ba92bd4..d328e05 100644
--- a/src/compiler/compiler_context.rs
+++ b/src/compiler/compiler_context.rs
@@ -8,4 +8,8 @@ impl HexoCompilerContext {
             safe_mode
         }
     }
+
+    pub(crate) fn safe_mode(&self) -> bool {
+        self.safe_mode
+    }
 }
diff --git a/src/compiler/hexo_compiler.rs b/src/compiler/hexo_compiler.rs
index 9c166db..ba04f3d 100644
--- a/src/compiler/hexo_compiler.rs
+++ b/src/compiler/hexo_compiler.rs
@@ -38,7 +38,7 @@ impl HexoCompiler {
         source: &TSource,
     ) -> Result<HexoFile, Error> {
         let cst = self.compile_cst(source)?;
-        let rst_compiler = RstCompiler::new(self);
+        let rst_compiler = RstCompiler::new(self, self.context.safe_mode());
 
         rst_compiler.compile(&cst).map_err(Error::Rst)
     }
diff --git a/src/compiler/native_fn/implementations.rs b/src/compiler/native_fn/implementations.rs
index 8d23f7c..1e0eceb 100644
--- a/src/compiler/native_fn/implementations.rs
+++ b/src/compiler/native_fn/implementations.rs
@@ -51,7 +51,7 @@ pub(crate) fn create_pad_right_native_function() -> NativeFunction {
 
 pub(crate) fn create_cmd_native_function() -> NativeFunction {
     NativeFunction::new(
-        NativeFunctionSignature::new("cmd"),
+        NativeFunctionSignature::new_unsafe("cmd"),
         |arguments, _| {
             let command = get_argument_at(&arguments, 0, "cmd")?
                 .to_string()
@@ -116,7 +116,7 @@ pub(crate) fn create_pad_native_function() -> NativeFunction {
 
 pub(crate) fn create_eval_native_function() -> NativeFunction {
     NativeFunction::new(
-        NativeFunctionSignature::new("eval"),
+        NativeFunctionSignature::new_unsafe("eval"),
         |arguments, compiler| {
             let buffer = get_argument_at(&arguments, 0, "eval")?.clone();
             let source = LiteralCompilerSource::anonymous(
diff --git a/src/compiler/native_fn/index.rs b/src/compiler/native_fn/index.rs
index c34ff21..6ba422a 100644
--- a/src/compiler/native_fn/index.rs
+++ b/src/compiler/native_fn/index.rs
@@ -7,6 +7,7 @@ pub(crate) struct NativeFunctionIndex {
 }
 
 impl NativeFunctionIndex {
+
     pub(crate) fn new() -> NativeFunctionIndex {
         NativeFunctionIndex {
             functions: Self::create_native_functions(),
@@ -14,7 +15,7 @@ impl NativeFunctionIndex {
     }
 
     pub(crate) fn find(&self, name: String) -> Option<&NativeFunction> {
-        return self.functions.iter().find(|f| f.signature().name == name);
+        return self.functions.iter().find(|f| f.signature().name() == name);
     }
 
     fn create_native_functions() -> Vec<NativeFunction> {
diff --git a/src/compiler/native_fn/signature.rs b/src/compiler/native_fn/signature.rs
index 91c0618..12e5e6d 100644
--- a/src/compiler/native_fn/signature.rs
+++ b/src/compiler/native_fn/signature.rs
@@ -5,15 +5,32 @@ use crate::compiler::HexoCompiler;
 
 #[derive(Clone, Debug)]
 pub(crate) struct NativeFunctionSignature {
-    pub(crate) name: String,
+    name: String,
+    is_safe: bool
 }
 
 impl NativeFunctionSignature {
     pub(crate) fn new(name: &str) -> NativeFunctionSignature {
         NativeFunctionSignature {
             name: String::from(name),
+            is_safe: true
         }
     }
+
+    pub(crate) fn new_unsafe(name: &str) -> NativeFunctionSignature {
+        NativeFunctionSignature {
+            name: String::from(name),
+            is_safe: false
+        }
+    }
+
+    pub(crate) fn name(&self) -> &str {
+        &self.name
+    }
+
+    pub(crate) fn is_safe(&self) -> bool {
+        self.is_safe
+    }
 }
 
 type NativeFunctionExecutor = fn(&HashMap<String, ByteBuffer>, &HexoCompiler) -> Result<ByteBuffer, Error>;
diff --git a/src/compiler/rst/compiler.rs b/src/compiler/rst/compiler.rs
index ba23cb8..def6ea3 100644
--- a/src/compiler/rst/compiler.rs
+++ b/src/compiler/rst/compiler.rs
@@ -14,11 +14,12 @@ use crate::util::id::HexoId;
 
 pub(crate) struct RstCompiler<'a> {
     parent: &'a HexoCompiler,
+    safe_mode: bool,
 }
 
 impl RstCompiler<'_> {
-    pub(crate) fn new(parent: &HexoCompiler) -> RstCompiler {
-        RstCompiler { parent }
+    pub(crate) fn new(parent: &HexoCompiler, safe_mode: bool) -> RstCompiler {
+        RstCompiler { parent, safe_mode }
     }
 
     pub(crate) fn compile(&self, cst: &CstFile) -> Result<HexoFile, Error> {
@@ -83,6 +84,14 @@ impl RstCompiler<'_> {
     ) -> Result<(), Error> {
         let native_function = context.get_native_function(function_name.as_str());
         if let Some(native_function) = native_function {
+            if self.safe_mode && !native_function.signature().is_safe() {
+                return Err(
+                    Error::NativeFunctionIsUnsafe {
+                        name: native_function.signature().name().to_string()
+                    }
+                )
+            }
+
             let executor = native_function.executor();
             let mut params_buffer = HashMap::new();
 
diff --git a/src/compiler/rst/error.rs b/src/compiler/rst/error.rs
index 544b35d..319e188 100644
--- a/src/compiler/rst/error.rs
+++ b/src/compiler/rst/error.rs
@@ -3,6 +3,7 @@ pub(crate) enum Error {
     UnresolvedConstant { name: String },
     UnresolvedFunction { name: String },
     NativeFunctionExecution(crate::compiler::native_fn::Error),
+    NativeFunctionIsUnsafe { name: String },
 }
 
 impl std::fmt::Display for Error {
@@ -17,6 +18,9 @@ impl std::fmt::Display for Error {
             Error::NativeFunctionExecution(e) => {
                 write!(f, "Native function execution error: {}", e)
             }
+            Error::NativeFunctionIsUnsafe { name } => {
+                write!(f, "Native function is unsafe: {}", name)
+            }
         }
     }
 }