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title: NULLs in entities in Firefox
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# NULLs in entities in Firefox

**NULLs in entities in Firefox** - Gareth Heyes, thespanner.co.uk.

- Published: date not stated
- Original: <http://www.thespanner.co.uk/2011/12/05/nulls-in-entities-in-firefox/>
- Current location: <https://thespanner.co.uk/2011/12/05/nulls-in-entities-in-firefox>
- Preserved from: https://thespanner.co.uk/2011/12/05/nulls-in-entities-in-firefox (stored) on 2026-08-17
- Licence: unknown

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## Content

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HTML5 decided to introduce a load of new entities, I dunno why maybe they thought it wasn't hard enough to protect against the original ones we had already. Anyway Firefox has a bug or "feature" that allows NULLS inside the entities. I tweeted it but if I don't post it here it will probably be lost in a sea of tweets. You can place NULLs before the "&amp;" or before the ";" which allows you to construct a pretty weird entity.

```javascript
javascript&0x00colon;
javascript&colon0x00;
```

These obviously work inside a anchor href and I think in addition FF requires the HTML5 doctype.