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Add tests demonstrating safe-mode unsafe link over-blocking #305

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Merged
jgm merged 2 commits into from
Jul 12, 2026
Merged

Add tests demonstrating safe-mode unsafe link over-blocking #305

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c9836d6
Add tests demonstrating safe-mode unsafe link over-blocking
GrahamCampbell Jul 12, 2026
ac8728e
Anchor all reUnsafeProtocol alternatives to the start of the URL
GrahamCampbell Jul 12, 2026
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2 changes: 1 addition & 1 deletion lib/render/html.js
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Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,7 @@
import { escapeXml } from "../common.js";
import Renderer from "./renderer.js";

var reUnsafeProtocol = /^javascript:|vbscript:|file:|data:/i;
var reUnsafeProtocol = /^(?:javascript|vbscript|file|data):/i;
var reSafeDataProtocol = /^data:image\/(?:png|gif|jpeg|webp)/i;

var potentiallyUnsafe = function(url) {
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65 changes: 65 additions & 0 deletions test/test.js
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Expand Up @@ -314,6 +314,71 @@ for (var j = 0; j < cases.length; j++) {
}
cursor.write("\n");

// safe mode
cursor.write("Safe mode:\n");

var writerSafe = new commonmark.HtmlRenderer({ safe: true });

var safeCases = [
{
name: "leading javascript: link is blocked",
input: "[link](javascript:alert(1))\n",
expected: "<p><a>link</a></p>\n"
},
{
name: "leading JAVASCRIPT: link is blocked",
input: "[link](JAVASCRIPT:alert(1))\n",
expected: "<p><a>link</a></p>\n"
},
{
name: "leading vbscript: link is blocked",
input: "[link](vbscript:msgbox(1))\n",
expected: "<p><a>link</a></p>\n"
},
{
name: "leading file: link is blocked",
input: "[link](file:///etc/passwd)\n",
expected: "<p><a>link</a></p>\n"
},
{
name: "leading data:text/html image is blocked",
input: "![img](data:text/html,x)\n",
expected: '<p><img src="" alt="img" /></p>\n'
},
{
name: "data: image is allowed",
input: "![img](data:image/png;base64,aaaa)\n",
expected: '<p><img src="data:image/png;base64,aaaa" alt="img" /></p>\n'
},
{
name: "https link containing data: is allowed",
input: "[link](https://example.com/view?src=data:image/png)\n",
expected:
'<p><a href="https://example.com/view?src=data:image/png">link</a></p>\n'
},
{
name: "https link containing file: is allowed",
input: "[link](https://example.com/download?to=file:report)\n",
expected:
'<p><a href="https://example.com/download?to=file:report">link</a></p>\n'
},
{
name: "https image containing vbscript: is allowed",
input: "![img](https://example.com/wiki/vbscript:_basics)\n",
expected:
'<p><img src="https://example.com/wiki/vbscript:_basics" alt="img" /></p>\n'
}
];

var safe_parse_and_render = function(z) {
return writerSafe.render(reader.parse(z));
};

for (var k = 0; k < safeCases.length; k++) {
pathologicalTest(safeCases[k], results, safe_parse_and_render);
}
cursor.write("\n");

cursor.write(
results.passed.toString() +
" tests passed, " +
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