fix: reject COUNT rules without DTSTART so limited automations cannot run forever (#27781)

backend/open_webui/constants.py

@@ -118,6 +118,9 @@ class ERROR_MESSAGES(str, Enum):
     AUTOMATION_TOO_FREQUENT = lambda interval='': f'Schedule too frequent. Minimum interval is {interval} seconds.'
     AUTOMATION_INVALID_RRULE = lambda err='': f'Invalid RRULE: {err}'
     AUTOMATION_NO_FUTURE_RUNS = 'RRULE has no future occurrences'
+    AUTOMATION_COUNT_REQUIRES_DTSTART = (
+        'RRULE with COUNT requires an explicit DTSTART line to anchor the occurrence window'
+    )
 
     FEATURE_DISABLED = lambda name='': f'{name} is disabled'
     INPUT_TOO_LONG = lambda size='': f'Input prompt exceeds maximum length of {size}'

backend/open_webui/utils/automations.py

@@ -124,6 +124,9 @@ def validate_rrule(s: str, tz: str = None) -> None:
     clock so that near-future schedules are not incorrectly rejected
     on servers whose system clock is ahead (e.g. UTC vs US timezones).
     """
+    upper = s.upper()
+    if 'COUNT=' in upper and 'DTSTART' not in upper:
+        raise ValueError(ERROR_MESSAGES.AUTOMATION_COUNT_REQUIRES_DTSTART)
     zi = _resolve_tz(tz)
     now = datetime.now(zi).replace(tzinfo=None) if zi else datetime.now()
     try: