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Fix XSS in safe_mode: image tags missing _safe_href check #744

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Fix XSS in safe_mode: image tags missing _safe_href check #744

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2 changes: 2 additions & 0 deletions lib/markdown2.py
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Expand Up @@ -3229,6 +3229,8 @@ def process_image(self, url: str, title_attr: str, link_text: str) -> Tuple[str,
This section will be skipped by the link processor
'''
img_class_str = self.md._html_class_str_from_tag("img")
if self.md.safe_mode and not self.md._safe_href.match(url):
url = ''

@Crozzers Crozzers Oct 19, 2026

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For links URLs are set to "#" if replaced by safe mode. Should be consistent here

result = (
f'<img src="{self.md._protect_url(url)}"'
f' alt="{self.md._hash_span(_xml_escape_attr(link_text))}"'
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9 changes: 9 additions & 0 deletions test/tm-cases/img_safe_mode_xss.html
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@@ -0,0 +1,9 @@
<p><img src="" alt="xss" /></p>

<p><img src="" alt="xss" /></p>

<p><img src="" alt="xss" /></p>

<p><img src="https://example.com/pic.png" alt="safe" /></p>

<p><img src="./images/pic.png" alt="safe" /></p>
1 change: 1 addition & 0 deletions test/tm-cases/img_safe_mode_xss.opts
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@@ -0,0 +1 @@
{"safe_mode": "escape"}
9 changes: 9 additions & 0 deletions test/tm-cases/img_safe_mode_xss.text
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@@ -0,0 +1,9 @@
![xss](javascript:alert(1))

![xss](JavaScript:alert(document.domain))

![xss](vbscript:MsgBox(1))

![safe](https://example.com/pic.png)

![safe](./images/pic.png)
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