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fix(core): WW-5623 HTML-encode form action in PostbackResult to prevent XSS #1653

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fix(core): WW-5623 HTML-encode form action in PostbackResult to prevent XSS #1653

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1b22424
fix(core): HTML-encode form action in PostbackResult to prevent XSS
tranquac Apr 6, 2026
721ef1c
fix(core): WW-5623 use StringEscapeUtils and add regression tests
tranquac Apr 9, 2026
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3 changes: 2 additions & 1 deletion core/src/main/java/org/apache/struts2/result/PostbackResult.java
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Original file line number Diff line number Diff line change
Expand Up @@ -23,6 +23,7 @@
import org.apache.struts2.inject.Inject;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import org.apache.commons.text.StringEscapeUtils;
import org.apache.struts2.dispatcher.mapper.ActionMapper;
import org.apache.struts2.dispatcher.mapper.ActionMapping;

Expand Down Expand Up @@ -104,7 +105,7 @@ protected void doExecute(String finalLocation, ActionInvocation invocation) thro

// Render
PrintWriter pw = new PrintWriter(response.getOutputStream());
pw.write("<!DOCTYPE html><html><body><form action=\"" + finalLocation + "\" method=\"POST\">");
pw.write("<!DOCTYPE html><html><body><form action=\"" + StringEscapeUtils.escapeHtml4(finalLocation) + "\" method=\"POST\">");
writeFormElements(request, pw);
writePrologueScript(pw);
pw.write("</html>");
Expand Down
103 changes: 103 additions & 0 deletions core/src/test/java/org/apache/struts2/result/PostbackResultTest.java
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Expand Up @@ -145,5 +145,108 @@ public void testPassingNullInvocation() throws Exception{
}
}

/**
* WW-5623: Verify that HTML special characters in finalLocation are properly
* escaped in the rendered form action attribute to prevent XSS.
*/
public void testFormActionHtmlEscaping() throws Exception {
ActionContext context = ActionContext.getContext();
ValueStack stack = context.getValueStack();
MockHttpServletRequest req = new MockHttpServletRequest();
MockHttpServletResponse res = new MockHttpServletResponse();
context.put(ServletActionContext.HTTP_REQUEST, req);
context.put(ServletActionContext.HTTP_RESPONSE, res);

// Push an object with a malicious property onto the value stack
stack.push(new Object() {
public String getTargetUrl() {
return "/test\"onmouseover=\"alert(1)";
}
});

PostbackResult result = new PostbackResult();
result.setLocation("/redirect?url=${targetUrl}");
result.setPrependServletContext(false);

IMocksControl control = createControl();
ActionInvocation mockInvocation = control.createMock(ActionInvocation.class);
expect(mockInvocation.getInvocationContext()).andReturn(context).anyTimes();
expect(mockInvocation.getStack()).andReturn(stack).anyTimes();

control.replay();
result.setActionMapper(container.getInstance(ActionMapper.class));

// Call doExecute directly with a malicious location containing all critical chars
result.doExecute("/test\"onmouseover=\"alert(1)\"&param=<script>", mockInvocation);

String output = res.getContentAsString();

// The action attribute must contain escaped HTML entities
assertTrue("Double quote should be escaped to &quot;",
output.contains("action=\"/test&quot;onmouseover=&quot;alert(1)&quot;&amp;param=&lt;script&gt;\""));
// Must not contain unescaped double-quote that breaks out of the attribute
assertFalse("Raw double-quote must not appear in action value",
output.contains("action=\"/test\""));

control.verify();
}

/**
* WW-5623: Verify that each individual HTML special character is properly escaped.
*/
public void testFormActionEscapesAllHtmlSpecialChars() throws Exception {
ActionContext context = ActionContext.getContext();
MockHttpServletRequest req = new MockHttpServletRequest();
MockHttpServletResponse res = new MockHttpServletResponse();
context.put(ServletActionContext.HTTP_REQUEST, req);
context.put(ServletActionContext.HTTP_RESPONSE, res);

IMocksControl control = createControl();
ActionInvocation mockInvocation = control.createMock(ActionInvocation.class);
expect(mockInvocation.getInvocationContext()).andReturn(context).anyTimes();

control.replay();

PostbackResult result = new PostbackResult();
result.setActionMapper(container.getInstance(ActionMapper.class));
result.doExecute("/path?a=1&b=2\"<>", mockInvocation);

String output = res.getContentAsString();

assertTrue("Ampersand should be escaped", output.contains("&amp;"));
assertTrue("Double-quote should be escaped", output.contains("&quot;"));
assertTrue("Less-than should be escaped", output.contains("&lt;"));
assertTrue("Greater-than should be escaped", output.contains("&gt;"));

control.verify();
}

/**
* WW-5623: Verify that a clean location (no special chars) renders unchanged.
*/
public void testFormActionCleanLocationUnchanged() throws Exception {
ActionContext context = ActionContext.getContext();
MockHttpServletRequest req = new MockHttpServletRequest();
MockHttpServletResponse res = new MockHttpServletResponse();
context.put(ServletActionContext.HTTP_REQUEST, req);
context.put(ServletActionContext.HTTP_RESPONSE, res);

IMocksControl control = createControl();
ActionInvocation mockInvocation = control.createMock(ActionInvocation.class);
expect(mockInvocation.getInvocationContext()).andReturn(context).anyTimes();

control.replay();

PostbackResult result = new PostbackResult();
result.setActionMapper(container.getInstance(ActionMapper.class));
result.doExecute("/clean/path/action.do", mockInvocation);

String output = res.getContentAsString();

assertTrue("Clean location should render as-is in action attribute",
output.contains("action=\"/clean/path/action.do\""));

control.verify();
}

}