Safe URLs in wiki

Hello,

In stdlib, there is a function that tests if a URL is "safe"

function IsSafeURL($url) {
     return !preg_match('/([<>"])|(%3C)|(%3E)|(%22)/', $url);
}

In practice, our users need to include in the wiki URLs generated by Live Meeting

https://www.livemeeting.com/cc/alcatel_lucent/join?id=4QPTFJ&role=present&pw=S%3Cpk%2F2fbS

and these URLs can contain %3C

What would be the risk to allow such URLs?

Best regards,

Marc-Etienne

-- 
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| Marc-Etienne Vargenau                                          |   /      \
| Alcatel-Lucent France, Route de Villejust, 91620 NOZAY, FRANCE |  /  /|'`  \
| +33 (0)1 30 77 28 33, [email protected]  | |  /'| '   |
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| L'essence des Mathématiques est dans leur liberté.             |   \      /
|                                Georges Cantor                  |    ------
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