Werk #12762: Fix several XSS issues

Component	User interface
Title	Fix several XSS issues
Date	May 7, 2021
Level	Trivial Change
Class	Security Fix
Compatibility	Compatible - no manual interaction needed
Checkmk versions & editions	2.1.0b1 Checkmk Community, Checkmk Pro, Checkmk Ultimate MT 2.0.0p4 Checkmk Community, Checkmk Pro, Checkmk Ultimate MT 1.6.0p25 Checkmk Community, Checkmk Pro, Checkmk Ultimate MT

• JavaScript was executed in the rule overview if a script was entered in the Text to match of EC rules.
• JavaScript was executed if scripts were entered in the LDAP server and failover server and "Save & Test" was clicked
• JavaScript was executed in the notification rules if sripts were entered in the the title and topic of aux tags and tags.

FEED-6031

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