mod_cloud_notify_encrypted: Ensure body substring remains valid UTF-8 The `body:sub()` call risks splitting the string in the middle of a multi-byte UTF-8 sequence. This should have been caught by util.stanza validation, but that would have caused some havoc, at the very least causing the notification to not be sent. There have been no reports of this happening. Likely because this module isn't widely deployed among users with languages that use many longer UTF-8 sequences. The util.encodings.utf8.valid() function is O(n) where only the last sequence really needs to be checked, but it's in C and expected to be fast.

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labels:
- 'Stage-Alpha'
summary: 'Require MUC occupant nicknames to match a specific pattern'
---

Introduction
============

This checks the nickname of a joining user against a configurable
[Lua pattern](https://www.lua.org/manual/5.2/manual.html#6.4.1), and prevents
them from joining if it does not match.

Configuration
=============

There is a single configuration option, `muc_restrict_nick_pattern` and the
default is `"^%w+$"` - i.e. allow only alphanumeric characters in nicknames.

Compatibility
=============

Requires Prosody 0.11 or higher.