Scenario:
1. Log in as Teacher, add activities with deadlines / closing dates, or activities with only opening dates (without closing dates), and / or set Expected completion dates.
2. Suspend a student in a course, or terminate their enrolment in the course by imposing his/her enrolment end date
3. Log in as the suspended / not current student and go to the Dashboard > Timeline.
4. See deadlines / closing dates (opening dates where relevant) and Expected completions dates for many activities which the suspended students should NOT see - clicking on the shown links will take the student to the course enrolment page, while the activity of course cannot be taken.

This leaky filtering affects the Timeline only. The filtering applied in the Calendar (and Upcoming events block where relevant) works correctly.

UPDATE 2018-11-17 21:32: Moodle 3.6 dev+: Timeline > Sort by dates is affected ONLY, whereas Timeline > Sort by courses correctly excludes those courses where the student is suspended / not current.

Expected completion date setting causes the Timeline leak for EACH activity and resource, as I have been able to establish.

As far as the Availability / Timing / Deadline settings, the following activities are affected (slip through for suspended students):

• Workshop - deadline for submission
• Workshop - opening date for submission (shown in Timeline when closing date is not set)
• Workshop - deadline for assessment
• Workshop - opening date for assessment (shown in Timeline when closing date is not set)
• Quiz - closing date
• Quiz - opening date (shown in Timeline when closing date is not set)
• SCORM closing date
• SCORM - opening date (shown in Timeline when closing date is not set)
• Database closing date
• Database opening date (shown in Timeline when closing date is not set)
• Choice closing date
• Choice opening date (shown in Timeline when closing date is not set)
• Lesson closing date
• Lesson opening date (shown in Timeline when closing date is not set)
• Feedback closing date
• Feedback opening date (shown in Timeline when closing date is not set)
• Chat - opening/first session date

The dates on which the report above is based were all dates in the future. 

This very detailed check was made when testing the Moodle 3.6 dev master version on 2018-11-15.

UPDATE 2018-11-17 21:45 : I have specifically tested 3.5.2 now and canNOT reproduce the problem, so my earlier report that this version is affected must stand corrected. I have therefore removed 3.5.2 from the affected versions.