Security researcher Juan Pablo Lopez Yacubian reported that the default Windows font used to render the locationbar and other text fields was improperly displaying certain Unicode characters with tall line-height. In such cases the tall line-height would cause the rest of the text in the input field to be scrolled vertically out of view. An attacker could use this vulnerability to prevent a user from seeing the URL of a malicious site.
Corrie Sloot also independently reported this issue to Mozilla.
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