Levente Uzonyi uploaded a new version of System to project The Trunk:
http://source.squeak.org/trunk/System-ul.1148.mcz

==================== Summary ====================

Name: System-ul.1148
Author: ul
Time: 24 March 2020, 9:15:28.593463 pm
UUID: 79bbf013-47f5-4f3c-9e42-8f169fe22a6c
Ancestors: System-ul.1147

- create a deep copy of the keys read from the file in SecurityManager >> #loadSecurityKeys, so that they can be modified later

=============== Diff against System-ul.1147 ===============

Item was changed:
  ----- Method: SecurityManager>>loadSecurityKeys (in category 'fileIn/out') -----
  loadSecurityKeys
  	"SecurityManager default loadSecurityKeys"
  	"Load the keys file for the current user"
  	| fd loc file keys |
  	self isInRestrictedMode ifTrue:[^self]. "no point in even trying"
  	loc := self secureUserDirectory. "where to get it from"
  	loc last = FileDirectory pathNameDelimiter ifFalse:[
  		loc := loc copyWith: FileDirectory pathNameDelimiter.
  	].
  	fd := FileDirectory on: loc.
  	file := [fd readOnlyFileNamed: keysFileName] 
  			on: FileDoesNotExistException do:[:ex| nil].
  	file ifNil:[^self]. "no keys file"
+ 	keys := (Object readFrom: file) veryDeepCopy. "Use #veryDeepCopy to make the non-writable literal objects created by the Compiler writable."
- 	keys := Object readFrom: file.
  	privateKeyPair := keys first.
  	trustedKeys := keys last.
  	file close.!