The exception has been changed after XWIKI-21119, the stack trace is now:
2025-07-18 13:19:13,722 [qtp79290965-128 - http://localhost:1750/xwiki/bin/get/XWiki/Extensions] ERROR a.i.BridgeAuthorizationManager - Failed to load rights for user [xwiki:XWiki.Admin] on [xwiki:XWiki.Extensions].
java.lang.ArrayIndexOutOfBoundsException: Index 15 out of bounds for length 15
at java.base/java.util.concurrent.CopyOnWriteArrayList.elementAt(CopyOnWriteArrayList.java:385)
at java.base/java.util.concurrent.CopyOnWriteArrayList.get(CopyOnWriteArrayList.java:398)
at org.xwiki.security.authorization.Right.get(Right.java:388)
at org.xwiki.security.authorization.RightSet$RightIterator.next(RightSet.java:114)
at org.xwiki.security.authorization.RightSet$RightIterator.next(RightSet.java:85)
at java.base/java.util.Collections$UnmodifiableCollection$1.next(Collections.java:1054)
at org.xwiki.security.authorization.internal.DefaultAuthorizationSettler.settle(DefaultAuthorizationSettler.java:61)
at org.xwiki.security.authorization.internal.AbstractAuthorizationSettler.settle(AbstractAuthorizationSettler.java:209)
at org.xwiki.security.authorization.internal.DefaultAuthorizationSettler.settle(DefaultAuthorizationSettler.java:46)
at org.xwiki.security.authorization.cache.internal.DefaultSecurityCacheLoader.loadAccessEntries(DefaultSecurityCacheLoader.java:191)
at org.xwiki.security.authorization.cache.internal.DefaultSecurityCacheLoader.load(DefaultSecurityCacheLoader.java:155)
at org.xwiki.security.authorization.DefaultAuthorizationManager.getAccess(DefaultAuthorizationManager.java:277)
at org.xwiki.security.authorization.DefaultAuthorizationManager.evaluateSecurityAccess(DefaultAuthorizationManager.java:194)
at org.xwiki.security.authorization.DefaultAuthorizationManager.hasSecurityAccess(DefaultAuthorizationManager.java:160)
at org.xwiki.security.authorization.DefaultAuthorizationManager.hasAccess(DefaultAuthorizationManager.java:112)
at org.xwiki.security.authorization.internal.BridgeAuthorizationManager.hasAccess(BridgeAuthorizationManager.java:67)
at org.xwiki.security.authorization.internal.DefaultContextualAuthorizationManager.hasAccess(DefaultContextualAuthorizationManager.java:131)
at org.xwiki.security.authorization.internal.DefaultContextualAuthorizationManager.hasAccess(DefaultContextualAuthorizationManager.java:126)
at org.xwiki.security.authorization.internal.DefaultContextualAuthorizationManager.hasAccess(DefaultContextualAuthorizationManager.java:118)
at org.xwiki.security.authorization.script.SecurityAuthorizationScriptService.hasAccess(SecurityAuthorizationScriptService.java:86)