GHSA-8rr6-2qw5-pc7r PMD Designer has Stored XSS in VBHTMLRenderer and YAHTMLRenderer via unescaped violation messages

• Maven net.sourceforge.pmd:pmd-core: < 7.22.0 → fixed in 7.22.0

Summary PMD's `vbhtml` and `yahtml` report formats insert rule violation messages into HTML output without escaping. When PMD analyzes untrusted source code containing crafted string literals, the generated HTML report contains executable JavaScript that runs when opened in a browser. While the default `html` format is not affected via rule violation messages (it correctly uses `StringEscapeUtils.escapeHtml4()`), it has a similar problem when rendering suppressed violations. The user supplied message (the reason for the suppression) was not escaped. Details `VBHTMLRenderer.java` line 71 appends `rv.getDescription()` directly into HTML: ```java sb.append("").append(rv.getDescription()).append(""); ``` `YAHTMLRenderer.java` lines 196–203 does the same via `renderViolationRow()`: ```java private String renderViolationRow(String name, String value) { return "" + name + "" + "" + value + ""; } ``` Called at line 172: ```java out.print(renderViolationRow("Description:", violation.getDescription())); ``` The violation message originates from `AvoidDuplicateLiteralsRule.java` line 91, which embeds raw string literal values via `first.toPrintableString()`. This calls `StringUtil.escapeJava()` (line 476–480), which is a Java source escaper — it passes ``, and `&` through unchanged because they are printable ASCII (0x20–0x7e). By contrast, `HTMLRenderer.java` line 143 properly escapes: ```java String d = StringEscapeUtils.escapeHtml4(rv.getDescription()); ``` PoC 1. Create a Java file with 4+ duplicate string literals containing an HTML payload: ```java public class Exploit { String a = ""; String b = ""; String c = ""; String d = ""; } ``` 2. Run PMD with the `vbhtml` format: ```bash pmd check -R category/java/errorprone.xml -f vbhtml -d Exploit.java -r report.html ``` 3. Open `report.html` in a browser. A JavaScript alert executes showing `document.domain`. The generated HTML contains the unescaped tag: ```html The String literal "" appears 4 times in this file ``` Tested and confirmed on PMD 7.22.0-SNAPSHOT (commit bcc646c53d). Impact Stored cross-site scripting (XSS). Affects CI/CD pipelines that run PMD with `--format vbhtml` or `--format yahtml` on untrusted source code (e.g., pull requests from external contributors) and expose the HTML report as a build artifact. JavaScript executes in the browser context of anyone who opens the report. Practical impact is limited because `vbhtml` and `yahtml` are legacy formats rarely used in practice. The default `html` format has a similar issue with user messages from suppressed violations. Fixes • See #6475: \[core] Fix stored XSS in VBHTMLRenderer and YAHTMLRenderer