CVE-2025-62780 - Stored XSS in Watch update via API

changedetectionio/html_tools.py

@@ -13,6 +13,7 @@ TITLE_RE = re.compile(r"<title[^>]*>(.*?)</title>", re.I | re.S)
 META_CS  = re.compile(r'<meta[^>]+charset=["\']?\s*([a-z0-9_\-:+.]+)', re.I)
 META_CT  = re.compile(r'<meta[^>]+http-equiv=["\']?content-type["\']?[^>]*content=["\'][^>]*charset=([a-z0-9_\-:+.]+)', re.I)
 
+SAFE_PROTOCOL_REGEX='^(http|https|ftp|file):'
 
 # 'price' , 'lowPrice', 'highPrice' are usually under here
 # All of those may or may not appear on different websites - I didnt find a way todo case-insensitive searching here
@@ -22,6 +23,21 @@ class JSONNotFound(ValueError):
     def __init__(self, msg):
         ValueError.__init__(self, msg)
 
+def is_safe_url(test_url):
+    import os
+    # See https://github.com/dgtlmoon/changedetection.io/issues/1358
+
+    # Remove 'source:' prefix so we dont get 'source:javascript:' etc
+    # 'source:' is a valid way to tell us to return the source
+
+    r = re.compile(re.escape('source:'), re.IGNORECASE)
+    test_url = r.sub('', test_url)
+
+    pattern = re.compile(os.getenv('SAFE_PROTOCOL_REGEX', SAFE_PROTOCOL_REGEX), re.IGNORECASE)
+    if not pattern.match(test_url.strip()):
+        return False
+
+    return True
 
 # Doesn't look like python supports forward slash auto enclosure in re.findall
 # So convert it to inline flag "(?i)foobar" type configuration